Organolithium alkynolates are one of the commonly used organolithium reagents. As shown in the reaction below, pre-prepared lithium propargyl alcoholate can be used to synthesize the natural product $\mathbf{A}$ with another substrate. Two key electroneutral intermediates $\mathbf{B}$ and $\mathbf{C}$ are formed during the formation of $\mathbf{A}$.
<MultiModal>![CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(OCC)=O)C2=O)=O)([H])C1和CC#CO[Li]反应可合成CC1=C2[C@@](CC1=O)(C)C([C@@]3([H])CC(C)(C)C[C@]32[H])=O](/media/uploads/3b5ec4f3-33d3-4059-b2ee-d790b3bba6fc.png)</MultiModal>
The following statements are available:
1. $\mathbf{A}$ and $\mathbf{B}$ have the same number of rings.
2. $\mathbf{A}$ and $\mathbf{C}$ have the same number of rings.
3. $\mathbf{B}$ and $\mathbf{C}$ have the same number of oxygen atoms.
4. $\mathbf{B}$ contains an alkynyl group.
5. $\mathbf{C}$ contains $\mathbf{4}$ double bonds.
6. Gas is released during the formation of $\mathbf{A}$.

Which of the above statements are correct:
有机炔醇锂是常用的有机锂试剂之一，如下图反应中，用预先制备的丙炔醇锂与另一底物可合成天然产物 $\mathbf{A}$ 。形成 $\mathbf{A}$ 过程中有两个关键电中性中间体 $\mathbf{B}$ 和 $\mathbf{C}$ 。
<MultiModal>![CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(OCC)=O)C2=O)=O)([H])C1和CC#CO[Li]反应可合成CC1=C2[C@@](CC1=O)(C)C([C@@]3([H])CC(C)(C)C[C@]32[H])=O](/media/uploads/3b5ec4f3-33d3-4059-b2ee-d790b3bba6fc.png)</MultiModal>
现有以下说法：
1. $\mathbf{A}$ 与 $\mathbf{B}$ 的环数相同。
2. $\mathbf{A}$ 与 $\mathbf{C}$ 的环数相同。
3. $\mathbf{B}$ 与 $\mathbf{C}$ 中氧元素的个数相同。
4. $\mathbf{B}$ 中含有炔基。
5. $\mathbf{C}$ 中含有 $\mathbf{4}$ 个双键。
6. 形成 $\mathbf{A}$ 过程中有气体放出。

以上说法正确的是：
1, 4
2, 3
2, 4
3, 5
3, 6
5, 6
6
1, 4
2, 3
2, 4
3, 5
3, 6
5, 6
6
The reaction mainly proceeds through three steps to obtain $\mathbf{A}$:

1.  In lithium alkynol, the alkyne terminal carbon connected to oxygen carries a positive charge, and the other end carries a negative charge. During the reaction, the electrons of the oxygen anion are transferred to form a lithium enolate of ketene, which promotes the negatively charged terminal carbon to attack the ester carbonyl carbonyl in another reactant. Ethoxy leaves, and a nucleophilic substitution reaction occurs to generate intermediate product $\mathbf{B}$. The chemical formula of $\mathbf{B}$ is:

<MultiModal>![CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(C(C)=C=O)=O)C2=O)=O)([H])C1](/media/uploads/f4aa917f-587f-4de7-9b56-a1f8ec0c8466.png)</MultiModal>

<Checkpoint>[A nucleophilic substitution reaction occurs, and the negatively charged terminal carbon in the ketene anion attacks the ester carbonyl carbonyl of another reactant.](1)</Checkpoint>

<Checkpoint>[The chemical formula of $\mathbf{B}$ is CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(C(C)=C=O)=O)C2=O)=O)([H])C1](2)</Checkpoint>

2.  There are two carbonyl groups on the ring in $\mathbf{B}$. Among them, the carbonyl group located at the top of the figure undergoes a [2+2] cycloaddition reaction with the carbon-carbon double bond in the ketene to form compound $\mathbf{C}$ with a four-membered ring and a five-membered ring. The chemical formula of $\mathbf{C}$ is:

<MultiModal>![O=C1[C@@]2([H])CC(C)(C)C[C@@]2([H])C3(O4)[C@]1(C)CC(C3(C)C4=O)=O](/media/uploads/c8aaedce-5026-47bd-8c0c-0c935ff2f18e.png)</MultiModal>

<Checkpoint>[A [2+2] cycloaddition reaction occurs, and the carbonyl group in $\mathbf{B}$ reacts with the carbon-carbon double bond in the ketene to form product $\mathbf{C}$.](1)</Checkpoint>

<Checkpoint>[The chemical formula of $\mathbf{C}$ is O=C1[C@@]2([H])CC(C)(C)C[C@@]2([H])C3(O4)[C@]1(C)CC(C3(C)C4=O)=O](2)</Checkpoint>

3.  The ester group in $\mathbf{C}$ undergoes an elimination reaction, producing $\mathrm{CO_2}$ gas and obtaining product $\mathbf{A}$ with a carbon-carbon double bond.

<Checkpoint>[An elimination reaction occurs, producing $\mathrm{CO_2}$ gas and a carbon-carbon double bond](1)</Checkpoint>

Therefore, the existing statements 3 and 6 are correct. Select option E.
该反应过程中主要经过三步反应得到 $\mathbf{A}$ ：
1. 炔醇锂中连接氧的炔基端基碳带正电，另一端带负电。反应时，氧负离子的电子打下来，形成烯酮的锂烯醇负离子，促使该带负电端基碳进攻另一反应物中的酯基羰基羰，乙氧基离去，发生亲核取代反应生成中间产物 $\mathbf{B}$ 。 $\mathbf{B}$ 的化学式为：

<MultiModal>![CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(C(C)=C=O)=O)C2=O)=O)([H])C1](/media/uploads/f4aa917f-587f-4de7-9b56-a1f8ec0c8466.png)</MultiModal>

<Checkpoint>[发生亲核取代反应，烯酮负离子中带负电的端基碳进攻另一反应物的酯基羰基羰。](1)</Checkpoint>

<Checkpoint>[$\mathbf{B}$ 的化学式为CC1(C)C[C@]2([H])[C@](C([C@@](C)(CC(C(C)=C=O)=O)C2=O)=O)([H])C1](2)</Checkpoint>

2. $\mathbf{B}$ 中环上有两个羰基。其中，处于图中上方羰基与烯酮中碳碳双键发生[2+2]环加成反应，形成带有四元环和五元环的化合物 $\mathbf{C}$ 。$\mathbf{C}$ 的化学式为：

<MultiModal>![O=C1[C@@]2([H])CC(C)(C)C[C@@]2([H])C3(O4)[C@]1(C)CC(C3(C)C4=O)=O](/media/uploads/c8aaedce-5026-47bd-8c0c-0c935ff2f18e.png)</MultiModal>

<Checkpoint>[发生[2+2]环加成反应， $\mathbf{B}$ 中羰基与烯酮中碳碳双键反应，形成产物 $\mathbf{C}$ 。](1)</Checkpoint>

<Checkpoint>[$\mathbf{C}$ 的化学式为O=C1[C@@]2([H])CC(C)(C)C[C@@]2([H])C3(O4)[C@]1(C)CC(C3(C)C4=O)=O](2)</Checkpoint>

3. $\mathbf{C}$ 中酯基发生消去反应，有 $\mathrm{CO_2}$气体生成，并得到带碳碳双键的产物 $\mathbf{A}$ 。

<Checkpoint>[发生消去反应，生成$\mathrm{CO_2}$气体和碳碳双键](1)</Checkpoint>

因此，现有说法正确的是3, 6。选择 E 选项。