I will not go to bed _______I finish watching my favourite TV programme.
A:since
B:until
C:after
D:when
—He ____ (swim).
读图回答问题.
两栖类是脊椎动物由____ 向____ 过度的类群,____ 类动物由于能在陆地上生活和生殖而成为真正的陆生动物.