The number of significant figures in 10.1 is 3 as there are two digits before the decimal and one digit after the decimal.
The number of significant digit in 100.05 is 5 as there are 3 digits before the decimal and two digits after the decimal.
The number of significant digits in 120 is 2.
The number of significant digits in 129 is 3.
Hence, the correct answers are (A) and (D)digit