In 1995, Professor Kim's research group reported the following reaction:

<MultiModal>![N1(CC1C2=CC=CC=C2)/N=C/C3C(C4=CC=CC=C4)O3 yields C#CC(C1=CC=CC=C1)O under heating conditions](/media/uploads/5b1f5fdd-34aa-4167-a055-ecc0a69acc42.jpg)</MultiModal>

Mechanistic studies have shown that, under heating conditions, the substrate molecule first decomposes to give $\bf{A}$ and $\bf{B}$, the molecular weight of $\bf{A}$ is approximately 104, $\bf{B}$ undergoes ring-opening to give $\bf{C}$, $\bf{C}$ undergoes intramolecular proton transfer to give $\bf{D}$, $\bf{D}$ then releases a molecule of gas to give $\bf{E}$, and $\bf{E}$ undergoes a 1,2-H shift to give the product.

The following statements are made:

1. The degree of unsaturation of $\bf{A}$ is 5

2. $\bf{B}$ is a 1,3-dipole

3. $\bf{C}$ has a charge-separated structure and the types of atoms bearing the positive and negative formal charges are different

4. The gas released by $\bf{D}$ is not a common gas in the atmosphere

5. All atoms in $\bf{E}$ (except hydrogen atoms) satisfy the octet rule

Which of the following options contains the most correct statements?
1995年，Kim教授课题组报道了如下反应：

<MultiModal>![N1(CC1C2=CC=CC=C2)/N=C/C3C(C4=CC=CC=C4)O3在加热条件下得到C#CC(C1=CC=CC=C1)O](/media/uploads/5b1f5fdd-34aa-4167-a055-ecc0a69acc42.jpg)</MultiModal>

机理研究表明，在加热条件下，底物分子先发生分解得到$\bf{A}$和$\bf{B}$，$\bf{A}$的分子量约为104，$\bf{B}$发生开环得到$\bf{C}$，$\bf{C}$发生分子内质子转移得到$\bf{D}$，$\bf{D}$再放出一分子气体得到$\bf{E}$，$\bf{E}$发生1,2-H迁移即可得到产物。

有以下说法：

1.$\bf{A}$的不饱和度为5

2.$\bf{B}$为1,3-偶极体

3.$\bf{C}$具有电荷分离的结构且正负形式电荷所在原子种类不同

4.$\bf{D}$放出的气体不是大气中常见气体

5.$\bf{E}$中所有原子（除氢原子）均满足八隅律

以下选项中包含正确说法最多的一项是
All statements are incorrect.
1,2,3
2,3,4
3,4,5
4,5
2,3,4,5
1,2
1,3
1,5
2,4
2,3,5
2,5
3,4
2,4,5
1,2,4
1,3,5
2,3,4
所有说法均错误
1,2,3
2,3,4
3,4,5
4,5
2,3,4,5
1,2
1,3
1,5
2,4
2,3,5
2,5
3,4
2,4,5
1,2,4
1,3,5
2,3,4
The 2-phenylaziridine ring in the substrate easily undergoes a ring-opening reaction upon heating, eliminating styrene. The molecular weight of styrene is exactly 104, therefore $\bf{A}$ is styrene.

<Checkpoint>[Elimination of the 2-phenylaziridine ring produces $\bf{A}$, $\bf{A}$ is styrene, with an unsaturation degree of 5, statement 1 is correct](1)</Checkpoint>

The structure of the remaining $\bf{B}$ is `[N-]=[N+]=CC1C(C2=CC=CC=C2)O1`, which is a 1,3-dipole.

<Checkpoint>[The structure of $\bf{B}$ is `[N-]=[N+]=CC1C(C2=CC=CC=C2)O1`, which is a 1,3-dipole, statement 2 is correct](1)</Checkpoint>

$\bf{B}$ undergoes ring-opening, and the negative charge on the nitrogen attacks and opens the epoxide ring, yielding $\bf{C}$: `[O-]C(C1=CC=CC=C1)/C=C\[N+]#N`, with formal charges located on nitrogen and oxygen, respectively.

<Checkpoint>[The structure of $\bf{C}$ is `[O-]C(C1=CC=CC=C1)/C=C\[N+]#N`, with formal charges located on nitrogen and oxygen, respectively, statement 3 is correct](1)</Checkpoint>

$\bf{C}$ undergoes intramolecular proton transfer to yield $\bf{D}$. The oxygen anion can abstract the hydrogen on the carbon atom attached to the diazo group, yielding `OC(C1=CC=CC=C1)/C=[C-]\[N+]#N`. Under heating conditions, the diazo group can decompose to produce nitrogen gas, which is the gas produced in the step from $\bf{D}$ to $\bf{E}$.

<Checkpoint>[$\bf{D}$ releases nitrogen gas when forming $\bf{E}$, which is a common gas in the atmosphere, statement 4 is incorrect](1)</Checkpoint>

After the departure of nitrogen gas, carbene $\bf{E}$ is generated in situ, with the structure `OC(C1=CC=CC=C1)C=[C]`. Subsequently, a hydrogen migration occurs, with an alkenyl hydrogen migrating to the carbene.

<Checkpoint>[$\bf{E}$ contains a carbene, and the carbene carbon atom does not satisfy the octet rule, statement 5 is incorrect](1)</Checkpoint>

Therefore, the correct statements are 1, 2, and 3. Choose option B.
底物中的2-苯基吖丙啶环很容易在加热时发生环开环反应，消除苯乙烯，苯乙烯的分子量恰好为104，因此$\bf{A}$为苯乙烯。

<Checkpoint>[2-苯基吖丙啶环消除产生$\bf{A}$，$\bf{A}$为苯乙烯，不饱和度为5，说法1正确](1)</Checkpoint>

剩余$\bf{B}$的结构为`[N-]=[N+]=CC1C(C2=CC=CC=C2)O1`，为1,3-偶极体

<Checkpoint>[$\bf{B}$的结构为`[N-]=[N+]=CC1C(C2=CC=CC=C2)O1`，为1,3-偶极体，说法2正确](1)</Checkpoint>

$\bf{B}$发生开环，氮上负电荷进攻打开环氧环，得到$\bf{C}$：`[O-]C(C1=CC=CC=C1)/C=C\[N+]#N`，形式电荷分别位于氮和氧上。

<Checkpoint>[$\bf{C}$的结构为`[O-]C(C1=CC=CC=C1)/C=C\[N+]#N`，形式电荷分别位于氮和氧上，说法3正确](1)</Checkpoint>

$\bf{C}$发生分子内质子转移得到$\bf{D}$，氧负离子可以夺取重氮所连碳原子上的氢，得到`OC(C1=CC=CC=C1)/C=[C-]\[N+]#N`，加热条件下重氮基团可以分解产生氮气，为$\bf{D}$生成$\bf{E}$一步产生的气体。

<Checkpoint>[$\bf{D}$生成$\bf{E}$时释放氮气，为大气中常见气体，说法4错误](1)</Checkpoint>

离去氮气后，原位产生卡宾$\bf{E}$，结构为`OC(C1=CC=CC=C1)C=[C]`，随后发生氢迁移，一个烯基氢迁移至卡宾处得到产物。

<Checkpoint>[$\bf{E}$中含有卡宾，卡宾碳原子不符合八隅律，说法5错误](1)</Checkpoint>

故正确说法为1,2,3，选择选项B