A single grain of sand occupies a volume of about 0.004 cubic millimeters. Based on your previous answer,

how many grains of sand are on Earth's beaches?

2 & 23

Explanation:

Calculate the number of grains in two steps.

First, calculate the volume of one grain of sand in cubic meters:

0.0044 mm3 ×  = .

Then, calculate the number of grains of sand on the beaches:

7 × 1011 m3 ×  = 2 × 1023 grains.

the answer is option a.

yes the answer is total mass in unchanged   : )