The answer is A. Environmental conditions are not always right to produce flowers and seeds for sexual reproduction.
Most plants are able to reproduce either way because even if the conditions aren't right for the plant, it can still make more flowers so it doesn't die out.
I hope this helps! :D
For number 3, Queen Victoria's children and Queen Elizabeth II's descendants are Edward VII, George V, George VI
for number 4, the descendants of Philip of Greece are Alice, Victoria of Hesse, Alice of battenburg
Because they are genetically diverse cells that are used in sexual reproduction