Answer:
A
Step-by-step explanation:
"Twice" as bright can translate into the mathematical expression "times 2", where for every year, you multiply the previous year's brightness by 2.
Since this is a rate (using multiplication) and not a common difference (not using addition), it must be an exponential <em>something</em>, so eliminate C.
Now, since 2 > 1, that means this is an exponential growth. Remember that if the rate r is less than 1, then it's decay; if r is greater than 1, then it's growth.
The answer is thus A.
