Answer
Instead of underlining the significant figures, I will only list them in the answer:
a) 5.08
b) 508
c) 5.080
d)5080
Work Step by Step
a&b) Any nonzero number is significant, and any zero in between two significant numbers are significant
c) All numbers involved in a scientific notation form of a number are significant
d) Same as a&b, and, additionally, trailing zeroes in a decimal number are significant
