Answer: A
The option A is the most accurate description of unknown gas density relative to other gases in the table.
Observe the table clearly and compare it with given density of unknown gas i.e., <em>0.0009 g/cm³ . </em>
In the table, it is given that
1. Hydrogen - 0.00009 g/cm³, which is less than 0.0009 g/cm³, because the value of hydrogen has four zeros after the decimal point on right side, (that is decimal zero places up to ten thousands) but when comparing the value of unknown gas, it has zeros up to thousands place only on right side.
Hence, while moving on right side of the decimal point, the number of zeros decreases the value of given number.
(0.00009 > 0.0009)
similarly observe the remaining values
2. 0.0009 > 0.00018 (Helium)
3. 0.0009 < 0.00122 (AIr)
4. 0.0009 < 0.00142 (Oxygen)
<em>So, answer is A. </em>
