We go to school in the morning. Do you go to school in the morning? Do you go to school or to the park in the morning? Where do you go in the morning? When do you go to school? We go to school in the morning, don't we?
Now six friends are students. Are six friends students now? Are six friends students or pupils now? How many friends are students now? When are six friends students? звучит каряво, но если бы я поставила вопрос к подлежащему, то получился бы другой вид вопроса, не специальный Now six friends are students, aren't they?
1) During this period the track structure has been substantially improved. One of the greatest improvements was the elimination of rail joints. In order to reduce the number of joints the rails are welded into continuous lengths.These continuous or long welded rails have greater strength and provide a smoother running of trains at far greater speeds. 2) Another improvement which has made it possible to increase speeds on railways is the use of concrete sleepers. Thus in some countries , concrete sleepers have replaced wooden ones on heavily used main lines because of their advantages. Concrete sleepers have a longer life and a far greater weight than those made of wood. The greater weight of concrete sleepers provides the greater stability of track. It is this factor which has greatly contributed to increased speeds.
ответ взял прямо из текста. Насколько я помню, так надо делать в подобных заданиях.