49.犯罪现场 the crime scene

48.每76年 every 76 years

47.采取措施解决问题

take measures to solve the problem

46.在接下来的十年里 in the next ten years

45.环境污染　 environmental pollution

44.重力原理　 the Law of Gravity

43.代替　 instead of

42.五岁的儿子　 a 5-year-old son

41.用完　 use up

40.是…样子 what was … like?