Question

By the time he realizes he____into a trap,it`ll be too late for him to do anything about it

Answer 1

has
walked
句子分析,by
the
time
到XX时候,
he
realizes,
到他意识到XX的时候,
he
(walk)
into
a
trap,
进入了陷阱,
it
will
be
too
late
for
him
to
do
anything
about
it.
那对他来说太晚了而不能做什么了.
所以句子的意思应该是到他意识到他进入了陷阱的时候,就太晚了.
为什么会太晚,当然要已经,要表示已经就是完成时.
另外,
he
realizes后面接的是一个宾语从句,宾语从句和正常的句子一样,有自己的主语谓语宾语,根据时态realizes分析,要是现在完成时