Product $A$ of the above reaction is

The major product of the reaction is:

How many $\sigma$ and $\pi$ bonds are present in the following?
$(a)$ $But-1-ene-3-yne$
$(b)$ $Buta-1,3-diene$
$(c)$ $CH_2=CH-C\equiv N$
$(d)$ $Propa-1,2-diene$
$(e)$ $1-butyne$ and $2-butane$

Which of the following reactions results in the formation of a pair of diastereomers?

$2CH_3-C(Ph)=CH_2 \xrightarrow{H-A (acid)} (A) (major)$
Product $(A)$ is:

$CH_3-C(CH_3)=CH_2 + (CH_3)_3CH \xrightarrow[273 \ K]{HF} C_8H_{18} (A)$
Unknown $(A)$ in the above reaction is: