Aclassmate finds that it takes 1.090 seconds for a tossed ball to touch ground. how many significant figures are in this measurement?

4

Explanation:

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Rules for significant figures:

Digits from 1 to 9 are always significant and have infinite number of significant figures.

All non-zero numbers are always significant. For example: 654, 6.54 and 65.4 all have three significant figures.

All zero’s between integers are always significant. For example: 5005, 5.005 and 50.05 all have four significant figures.

All zero’s preceding the first integers are never significant. For example: 0.0078 has two significant figures.

All zero’s after the decimal point are always significant. For example: 4.500, 45.00 and 450.0 all have four significant figures.

All zeroes used solely for spacing the decimal point are not significant. For example : 8000 has one significant figure.

Thus 1.090 has four significant figures as all the digits are significant.

a is the correct answer