Question

black mambas are fast, aggressive, and venomous. it is no wonder that they are considered one of the deadliest snakes in the world. in general, the snakes actually try to avoid confrontation. however, a perceived threat to a black mamba will result in several reactions meant to warn a potential victim. first, the black mamba raises its head, spreads out its neck - flap, opens its black mouth, and hisses. a threat that continues will lead to a more dangerous reaction: the mamba will bite its victim repeatedly, injecting its poisonous venom. for most of history, a mamba bite would mean certain death. today, though, an effective antivenom is available. match causes with their effects. black mamba perceives a new threat. black mamba perceives a continuing threat. cause effect black mamba hisses. black mamba injects victim with venom.

Explanation:

The text states that when a black mamba perceives a threat, it first raises its head, spreads its neck - flap, opens its black mouth, and hisses. This is the reaction to a new or initial threat. When the threat continues, it will bite its victim repeatedly and inject its venom.

Answer:

Black mamba perceives a new threat. → Black mamba hisses.
Black mamba perceives a continuing threat. → Black mamba injects victim with venom.