Aprotein channel, like the peripheral and integral proteins, is a transport protein that

A protein channel is a transport protein that helps larger molecules, that would otherwise not be able to diffuse through the membrane of a cell to move in or out of the cell depending on the concentration gradient.

Nimbostratus is the correct answer.
explanation: nimbostratus clouds are the type of clouds that are mostly likely present on gray, rainy day. these clouds produce continuous rain, snow and there is no thundering or lightening either.