I am pretty sure that the statement which is true is A. a molecule having a covalent bond can be ionic. I choose this option because you usually ca see how electons of polyatomic ions are being covalenr and gain or loose ionic electrons in order to accomplish the octet.<span>
</span>Do hope you find it helpful! Regards.
Volume of air = 1200 ml
<h3>Further explanation</h3>
Given
20% Oxygen in air
240 ml Oxygen
Required
Volume of air
Solution
The concentration of a substance can be expressed in several quantities such as moles, percent (%) weight / volume,), molarity, molality, parts per million (ppm) or mole fraction. The concentration shows the amount of solute in a unit of the amount of solvent
240 ml = 20% Oxygen
volume of air :
= 100%/20% x 240 ml
= 1200 ml