英语短文改错题,
请帮做下,最好能有解析,
Markisamiddleschoolstudent.Helivedinthemiddleofthetown.AboutamilefromMark'sbuilding,therehavemanyoldhouses.Theyareallemptyandgoingtobepullingdown.Hisfathersaystheyaredangerousandtellshimtokeepawayfromthem.Butheenjoysplayinghereverymuch.OneFridayontheirwayhomefromschool,Markwentintooneoftheemptyoldhouses.Hesawadoorleadingasmalldarkroom.Hewentintotheroomtoseewhathecouldfindthem.Justthenheheardaterriblesound.Theroofoftheoldhousefelloff.Marktiredtoopenadoor.However,hecouldn't.Buthehadtostaythere.Markwassavedthreedayslatebysomepoliceman.Theyuseddogstofindhim.