First, factor out the greatest common factor.
3a4−48b8
3(a4−16b8)
Factor using difference of squares.
3(a2−4b4)(a2+4b4)
Repeat.
3(a−2b)(a+2b)(a2+4b4)
You may be tempted to expand the answer choices or trying random numbers for a and b as mentioned in the previous question.
For this question, these strategies don't work because several answer choices are equivalent to the initial expression, just not completely factored.