Most of the evidence was destroyed in the fire. ____, it would be almost impossible to prove his guilty. [ ]

A. However

B. Otherwise

C. Therefore

D. Besides

城市生活垃圾的来源，主要来源于人们的____________，也有相当一部分来源于____________、机关、____________、商业等行业以及城镇露天公共场所，也混有小部分建筑垃圾。