1a. People who move out of a city because it is too crowded to an area where there is more space. 1b. People who move out of a city to an area where there is more space because it is too crowded. 1c. Because it is too crowded people who move out of a city to an area where there is more space. 1d. Because a city is too crowded people who move out of it to an area where there is more space. 1e. Because a city is too crowded people move out of it to an area where there is more space. 1f. Because it is too crowded people move out of a city to an area where there is more space. 1g. An area where there is more space people move out of it to because a city is too crowded. 1h. An area where there is more space people move out of a city to because it is too crowded. Question: Which is \are grammatically correct of all sentences above? I privately think these five (1a, 1b, 1e, 1f, 1h. ) are grammatically correct， but I have no confidence to decide whether or not they are correct.