1) I think 15 choose (d)
2) The choose (C) -4fg+4g
3) The choose (d) 3xy/2
4) The choose (a) ab/6
5) The choose (C) 2p+4q-6
6)
Point 6 I think there is an error because the unit m must be m³ because it is r² (m²) and h(m) becomes m³.
I hope I helped you^_^