The correct option is C 0.1 < 0.5 < 0.7 < 0.9
According to their places on the number line,
0 is at one place left of decimal to every number i.e., at units place.
Then one place to the right of the decimal(i.e., tenths place) we have 1, 9, 5, 7.
i.e., 1 < 5 < 7 < 9
According to their places on the number line,
0.1 < 0.5 < 0.7 < 0.9