A：放弃求生的念头，直接沉入水底
B：大声叫喊求救
C：保持冷静，等待救援
“One tree can't make a forest” tells us no one would be heroes ____ (with) his friends.
家庭电路的电压为____V，家庭电路中，开关与其所控制的用电器是____的，插座与插座之间是____的。（选填“串联”或“并联”）
