Instead, she must fend for herself. 所以它必须自己保护自己
adult females must still return to dry land to lay their eggs. 每年仍要返回干燥的陆地上产卵
Mammals must fight for their lives, 哺乳动物必须为生存而战
He must frequently stop to get his bearings 在追逐猎物的过程中
she must run the gauntlet of defensive mothers keen to protect their young. 它必须穿过一长排保护心极强的母龙