Answer
e) $1\times10^{-5}$
Work Step by Step
$(6.266-6.261)\div522.0 = 0.005\div522.0$
Here, 0.005 is the operand with the least significant figures.
Number of significant figures in 0.005 = 1.
The final answer should be rounded to one significant figure.
Hence, $0.005\div522.0$ = $1\times10^{-5}$