A6. A sequence of numbers is constructed as follows:

The first number is 2. The second number is 2.

Each subsequent number is the product of its two predecessors.

The sequence thus becomes: $2, 2, 4, 8, 32, \ldots$

What is the last digit of the $2007^{\text{th}}$ number in this sequence?
(A) 0
(B) 2
(C) 4
(D) 6
(E) 8
A6. We continue the row with only the last digits of the numbers: we find

$2,2,4,8, \cdot 2, \cdot \cdot 6, \cdot 2, \cdot \cdot 2, \cdot 4, \cdot 8, \cdot 2, \cdot 6, \cdot 2$, etc. We see that a group of six digits repeats itself. Since $2007=334 \times 6+3$, the last digit of the 2007th number is the same as that of the third number, which is 4. (C).