Answer: C

Since $1.44 = 1.2^2$, $(1.44)^t = (1.2^2)^t = (1.2)^{2t}$. So $500(1.44)^t = 500(1.2)^{2t}$. This form shows that the number of fish is multiplied by $1.2$, a $20\%$ increase, every half year.

Choice D splits the $44\%$ yearly growth into two equal $22\%$ steps, but $1.22^2 = 1.4884$, not $1.44$.

Why the other choices are wrong

• A. This halves the base 1.44. Doubling the exponent requires the square root of the base, 1.2, not half of it.
• B. This halves the exponent instead of doubling it. (1.2) to the power t/2 grows much more slowly than (1.44) to the power t.
• D. This splits the 44% growth into two 22% steps, but 1.22² = 1.4884, not 1.44.