28. Carbon dioxide is heavier than air. The gas is collected in the 'laboratory by A. Upward delivery B. Downward delivery C. Downward displacement D. Passing over water

C. Downward displacement<br /><br />Carbon dioxide is denser than air. Downward displacement (or downward delivery) is the method used to collect gases denser than air. The gas is delivered through a tube to the bottom of a collection jar, where it displaces the lighter air upwards.<br />