Which one of the following organic compounds decolourizes an alkaline $KMnO_4$ solution?

What is the product of Hydroboration-oxidation of but-$1$-ene?

Consider the following reactions. What is $A$?
| Reaction | Observation |
| :--- | :--- |
| $A \ (C_7H_{14}) \xrightarrow{\text{ozonolysis}} B + C$ | |
| $B \xrightarrow{I_2 + NaOH, \Delta} \text{yellow ppt}$ | |
| $B \xrightarrow{Ag_2O, \Delta} \text{silver mirror}$ | |
| $C \xrightarrow{I_2 + NaOH, \Delta} \text{no yellow ppt}$ | |
| $C$ $\xrightarrow{LiAlH_4} D$ $\xrightarrow{\text{anhydrous } ZnCl_2, \text{conc. } HCl} \text{white turbidity within 5 minutes}$ | |

Arrange the following compounds in the decreasing order of their reactivity towards electrophilic addition of $HBr$:
$(a)$ $CH_3-C(CH_3)=CH_2$
$(b)$ $CH_3O-C(CH_3)=CH_2$
$(c)$ $CH_3OCH_2-C(CH_3)=CH_2$

Assertion $(A)$: Propene on addition with hydrogen bromide in the presence of peroxide gives $1-$bromopropane as the major product.
Reason $(R)$: $1-$bromopropane is the major product because it is formed through the stable carbocation.
The correct answer is

Consider the following molecule $(X)$. The reaction of $(X)$ with $HBr$ gives the major product: