Among Known Plant Species, Which of These Have Been the Two

Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species?
1) allopatric speciation
2) sympatric speciation
3) sexual selection
4) polyploidy

A) 1 and 3
B) 1 and 4
C) 2 and 3
D) 2 and 4