Since a < 0, it is a negative number. Since b > 0, it is a positive number. So, we know the relationship between the two in terms of directionality. However, we're not given any info on their magnitude; i.e., whether their absolute values are equal, or one is greater than the other.

Since we're comparing numbers of unknown magnitude, the answer is D.

Examples with actual numbers to demonstrate:
Let a = -1 and b = 5
Quantity A = -2(-1+5) = -8
Quantity B = -(-1 * 5) = 5
B > A

Let a = -5 and b = 5
Quantity A = -2(-5+5) = 0
Quantity B = -(-5 * 5) = 25
B > A

Let a = -5 and b = 1
Quantity A = -2(-5+1) = 8
Quantity B = -(-5 * 1) = 5
A > B