A) Natural convection can take place in gravity free region    B) Forced convection is the principle in maintaining constant temperature of our body.

When temperature of air increases, its density decreases. So this light air rises up creating vaccum. This vaccum is filled up by cold heavier air coming from top and sides under the action of convection is not possible.But using a fan and blower, circulation of air can be maintained. This is forced convection.