(A) 10-15 billion years
(B) 15-20 billion years
(C) 20-30 billion years
(D) 30-40 billion years
The answer is: (A) 10-15 billion years
(A) 10-15 billion years
(B) 15-20 billion years
(C) 20-30 billion years
(D) 30-40 billion years
The answer is: (A) 10-15 billion years