During a lab experiment, students are supposed to add small pieces of magnesium, aluminum, and calcium metal to concentrated hydrochloric acid in a test tube. The laboratory instructions include strong safety warnings to make sure that no sparks, open flames, or high heat sources are present in the room when students perform this experiment. Which is the most likely reason for these warnings?

Hydrogen gas is highly flammable.

Heat may cause the hydrochloric acid to break down.

Heat can cause the acid to produce a salt.