People usually use umbrellas to protect themselves from sunshine and rain.(1楼同学错在不能用"ALWAYS",ALWAYS的频率几乎是100%,并非表示通常)
He denied that he was a policeman.He didn't admit that he was a policeman(1楼同学不能直接用a police.police是个集体名词,表示警察这个群体)
He spent 10 yuan on the magazine./He paid 10 yuan for the magazine./This magazine cost him 10 yuan(这里cost是过去式,所以不加s)
Finally,he has worked out this difficult problem successfully.(1楼同学译法也可,但时态最好用现在完成时)
He admitted that he hadn't done his homework.(1楼错在从句的时态,最好用过去完成时)
He lives alone,but he doesn't feel lonely.(注意alone 和 lonely区别)