(N/A) $1$. During winter,the air is dry,meaning it has low humidity.
$2$. When synthetic clothes are removed,they rub against the body or other layers of clothing,causing the transfer of electrons due to friction (triboelectric effect).
$3$. This process results in the accumulation of static electric charges on the surface of the synthetic fabric.
$4$. Because the air is dry,it acts as a poor conductor,allowing the charge to build up to a high potential difference.
$5$. When the potential difference becomes high enough,it causes a momentary breakdown of the air's insulating property,leading to a rapid discharge of electricity in the form of a spark,which is visible in the dark.