suppose 在什么情況下要用虛擬語(yǔ)氣？如Nancy is supposed to (做完化學(xué)實(shí)驗(yàn))　at least two weeks ago.

你好！
supposing/suppose
作連詞，可以虛擬，可以不虛擬
suppose
that....后面不用虛擬的
supposing/suppose
something
should
go
wrong,what
would
you
do?
如有疑問(wèn)，請(qǐng)追問(wèn)。

Nancy
is
supposed
to
(做完化學(xué)實(shí)驗(yàn))　at
least
two
weeks
ago.
這句話(huà)不是用不用虛擬語(yǔ)氣，因?yàn)槭遣欢〞r(shí)用現(xiàn)在時(shí)還是完成時(shí)的問(wèn)題,單獨(dú)來(lái)看2種情況都可能成立，適用于不同語(yǔ)境下。
at
least
two
weeks
ago至少兩周以前，這句話(huà)有責(zé)備的含義，使用完成時(shí)表示她應(yīng)該做什么（而沒(méi)做），2周前她就被告知做什么。Nancy
is
supposed
to
have
finished
the
chemistry
experiments
at
least
two
weeks
ago.
Nancy
is
supposed
to
finish
the
chemistry
experiments
at
least
two
weeks
ago.
責(zé)備的含義就弱了很多。差別在這里。
希望對(duì)你有所幫助。