Answer: C. He is afraid that the gods are angry and something bad will happen.
At the beginning of Act I, Scene III, we see Casca and Cicero on a Roman street. Casca is telling Cicero about the thunderstorm, and all the strange things he witnessed. He tells Cicero he saw a man with his hands on fire, a lion near the Capitol and an owl in the marketplace during the day. He is worried, as he believes both the weather and the strange events to be bad omens. He is afraid that the gods are angry, and that something bad is going to happen.