一、原因
1.A number of factors
are accountable for
this situation.
A number of factors
might(largely)contribute to (lead
to )
(account for ) t
he phenomenon(problem)./
被动The change in ...largely results from the fact that...
2. The answer to this problem
involves
many factors.
3. The phenomenon mainly
stems from
the fact that...
6. We may blame
...,but
the real causes are...
7. Part of the explanations for it is that ...
One of the most common factors (
causes )
is that ...
Another
contributing
fact ...