______ (他在事故中幸免于难) is really a miracle.

A. academic standard is improved by the education sector
B. there are comparable schools with different educational qualities
C. students have different interests in different courses
D. schools of all areas have sufficient budget for their development

A. Wind power needs to be fully understood before it can develop.
B. Suitable sites for wind power generation are hard to find.
C. There is not enough wind power for the whole country.
D. Only little research has been done on wind power.