Which plant structures are common to all angiosperms?
1:spores
2:flowers
3:cones
4:endoskeleton

3. cones

Explanation:

Gymnosperm seeds are often configured as cones.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.