The density of hydrogen is _____ times the density of air.

0.07
1.5
2.5
3.5

The correct answer is A. 0.07.

The density of hydrogen is 0.0789 g/L, while the density of air is 1.293 g/L. This means that hydrogen is about 1/17 times as dense as air.

Option B is incorrect because 1.5 is not the correct factor by which the density of hydrogen is less than the density of air.

Option C is incorrect because 2.5 is not the correct factor by which the density of hydrogen is less than the density of air.

Option D is incorrect because 3.5 is not the correct factor by which the density of hydrogen is less than the density of air.