AMC8 1985 Problem 8

If a=-2, the largest number in the set \left\{-3 a, 4 a, \dfrac{24}{a}, a^{2}, 1\right\} is

Answer Choices
A. -3 a
B. 4 \mathrm{a}
C. \dfrac{24}{a}
D. \mathrm{a}^{2}
E. 1