Thank you for reporting, we will resolve it shortly
Q.
The $ BCl_3$ is a planar molecule whereas $NCl_3$ is pyramidal because
AIPMTAIPMT 1995The p-Block Elements
Solution:
$BCl_3$ have $sp^ 2$ hybridisation and no lone pair of electron on central atom but $NCl_3$ have $sp^3$ hybridisation and also contains one lone pair of electron on nitrogen, so $BCl_3$ is planar.