(i) Element B and C belong to same group since both have same number of valence electrons in the outermost shell = 1
B = 2, 1
C = 2, 8 ,1
(ii) Elements in the order of decreasing atomic mass: A < D < B < C
A = 32
B = 22.9
C = 6.9
D = 32
(iii) B will form oxide with formula: B2O
(iv) D is a metalloid
(v)D belong to group 14.
Whenever an element of group 14, 15, 16 and 17 combine together, they form covalent bonds.
But whenever and element of group 14, 15, 16 or 17 combines with any element from group 1,2 or 13; ionic bonds are formed.