What is the boundary between two air masses called? Please help ASAP

A continental air mass
B cyclic boundary
C weather front
D cumulus stage

What must be true for natural selection to heppen

The finches on the galapagos island were similar in form except for variations of their beaks. darwin observed that these variations were useful for: attracting a mate defending territory building nests gathering food

Homo heidelbergensis was a tall, muscular hunter, who used both tools and weapons. because h. heidelbergensis was not a gatherer/forager, but ate a varied diet including meat and fish, we would expect to see what anatomical changes?