【简答题】What is important to do before going on a trip? How many reasons does the write mention? What is the first reason? When you answer these questions, what can you do? What can you find on the Internet?
【简答题】In neuron-to-neuron synaptic transmission, when a nerve impulse reaches the terminal bouton of the presynaptic neuron, it causes the terminal bouton to secrete ( ) into the synaptic cleft.