What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?

Answer: Option C

Clearly, the numbers which have 1 or 9 in the unit's digit, have squares that end in the digit 1.
Such numbers from 1 to 70 are 1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.
Number of such number = 14
$$=\left(\frac{14}{70}\times 100\right)\%=20\%$$