Lightning a. occurs when a positively charged cloud base induces a negative charge on the Earth's surface. b. travels most often from cloud to ground and cannot travel from cloud to cloud. c. may be accompanied by the sound of explosively expanding hot air, called thunder. d. involves a conductive path or leader of positive ions from cloud to ground.

c. may be accompanied by the sound of explosively expanding hot air, called thunder.

Explanation:

Lightning is a discharge which is due to the reaction between oppositely charged charges in the clouds, or between clouds base and the Earth surface.

The motion of the cloud causes charging of clouds by friction, thus the reaction between opposite charges (jumping of charges from one cloud to another) in the cloud can lead to lightning. Also, oftentimes the bottom of a cloud is negatively charged so that this is attracted to the positive charge on the earth surface. Thus leading to a discharge called lightning.

Thus in the given question, the appropriate option is C. This implies that, lightning may be accompanied by the sound of explosively expanding hot air, called thunder.