What Did Charles Darwin Investigate While Visiting the Galapagos Islands

What did Charles Darwin investigate while visiting the Galapagos Islands?

A) How the island species were completely different.
B) How the island species resembled those from nearby islands.
C) How the island species resembled those on other arid islands.
D) How the island species resembled those from continental South America.
E) How the islands were inhabited at all since they were 600 miles away from South America.