Answer:
1,048,576
Explanation:
We can tell that this is a geometric sequence because each new term is a multiple of the previous term. The common ratio is -2.
The pertinent formula is a(n) = -2 · (-2)^(n-1).
Thus, the 20th term of this sequence is a(20) = -2 · (-2)^(20-1), or
a(20) = -2 · (-2)^19, or 2^20, which comes out to 1,048,576 (same as the fourth possible answer).