1.While—When或After
本句的this指代的是to change the weather by using magic. when/after 引导时间状语
2.in—than
earlier是early的比较级，其后应有than
3.those之后加who
who引导定语从句
4. 删除advance前的the
in advance为习语
5. take—have
have connection with 为习语
6. controlled—controlling或在controlled前加that/which
controlling the weather 或that/which controlled the weather做定语修饰the actual factors
7. and—or
rain和draught只能是二者之一
8. 删除is
与上文平衡，均为省略句
9. before—when/if
条件句
10. will—would
if引导的是条件句用的是remained一般过去时