A number of factors might contribute to （lead to ）（account& bspfor ） the phenomenon（problem）.

　　2.　The answer to this problem involves many factors.

　　3.　The phenomenon mainly stems from the fact that……

　　4. The factors that contribute to this situation include……

　　5. The change in ……largely results from the fact&n spthat……

　　6. We may　blame ……,but the real causes are……

　　7. Part of the explanations for it is that ……【外语@教育网wwwwww.for68.com】

　　One of the most common factors （causes ） is that ……

　　Another contributing factor （cause ） is ……

　　Perhaps the primary actor is that …

　　But the fundamental cause is that ……