Which of the following is correct w.r.t. hydrides of elements of 15th group?

acidic character increases from NH3 to BiH3 thermal stability decreases .reducing character increases from NH3 toBiH3 because to M-H bond strength decreases due to increase in the size of the central atom.shape of tri hydrides of  15'th group elements is pyramidal.B.P increases down the group with increase in molecular mass but ammonia has high melting point due toN-H hydrogen bonding