A. I think sorry if it’s wrong
If you take your mom's advice, a. the room will be cooled by minimizing heat transfer by reflection.
The Sun is heating your room by its <em>radiation</em>.
The aluminium foil is shiny, so it reflects the Sun’s radiation back outside the window.
<em>Convection</em> is the transfer of heat caused by the air moving around in your room.
<em>Conduction</em> occurs only when a hot object is in contact with a cooler object.
Bromine has one more electron shell than the chlorine atom making the radius larger than the chlorine atom.