请问,This is a photograph I took during my trip to Australia.这句是定语从句吧?为什么不用“the ” 而用“a”呢?相同的，They are people I met during the trip.怎么不用 the

请问this is hard work 和 this is a hard work 有何区别 请问：is there a fast food resturant in this This is a orange orange.This is an orange orangeThis is a orange orange.This is an orange orange.请问哪句正确? Is this a book? Yes,this is. This is a man提问( ) is this? This is a love this is a japan This is a this is a This is a book this is a Demo This is a secret This is a story This is a This is a n_____jacket is this a jacket This is a cirde. This is a