The answer is E4.
The sequence is a geometric sequence with a common ratio of 2. This means that each term is 2 times the term before it.
F2, (2)(F2), (2)(2)(F2), (2)(2)(2)(F2), ...
F2, 2F2, 4F2, 8F2, ...
F2, 4, 8, 16, ...
The missing term is therefore E4.
