sustain
vt.保持;供养，维持;支持;经受
She found it difficult to sustain the children’s interest.她发现很难维持孩子们的兴趣。
swarm
n.蜂群，一大群 vi.云集;成群地飞行
Swarms of tourists jostled through the square.一群群游客推推挤挤穿过广场。
swear
v.诅咒，咒骂;宣誓，发誓
Don’t swear in front of the children.不要在孩子们面前说粗话。
