The mass of an object is reported as 5.20 g +0.05g. 0.05 g indicates the

I am thinking there is an error in or sign. it is supposed to be  ± instead of st + as in 5.20 g  ± 0.05g.

0.05 g indicates the Measurement of Uncertainty

The mass of an object is reported as 5.20 g  ±0.05g.

 Here , the  Measurement of Uncertainty  ±0.05g. explains that Random error always occur when taking measurements reading with any scale.This tells us that the object's correct reading is between 5.15 g and 5.25 g from 5.20 g- 0.05g. and 5.20 g + 0.05g respectively.

See here on measrement of uncertainty:  link

Atomic number.

Because 2 values given here are 0.05g and one is 5.20g. So there are 2 atoms of one element or compound and one atom of another element or compound.

answer

i think the answer is a) as air pressure in an area increases, the density of the gas particles in that area decreases.

hope it

elements make up everything, and they combine to make compounds.

the answer is c