Kumar gave his informative speech on meteorology. as part of the speech, he displayed an excellent drawing to indicate the temperatures in different layers of the atmosphere. when he got to the drawing, he said, "as you can see, each layer has a different temperature." he then covered up the drawing and quickly moved on. what should kumar have done to present his visual aid more effectively?

The answer is "He should have explained the visual aid more fully."

Giving a speech can be nerve-wracking, and it may appear to be anything but difficult to simply skirt the visual aids. 
A visual aid is something that supplements words with a photo, diagram, or delineation. Taking a gander at a picture of the mind and the optic nerve as you read about it is a decent case of a visual guide. It is a supplement to the words you're perusing.

Kumar should have explained the visual aid more fully.

Visual aids are illustrative. It is designed to assist written or spoken information. For it to be able to supplement the discussion, it has to be explained thoroughly. Explanation will maximize the potential of the material to aid in the presentation.