Factor marking brainiest 81x^6y^2-0.36a^2

is the difference of two squares, just like (a) (above); its factors are:  

(9x^3y - 0.6a)(9x^3y + 0.6a)

Explanation:

for those of you who searched "which list includes four types of animal-like protists? " and keep getting these results, the answer is c: flagellates, sarcodines, ciliates, parasites