Can I say,<br/><br/>(a) The log is floating in the river.<br/><br/>(b) Ice skating is John's hobby.<br/><br/>(c) He is working at / in the hotel. <br/><br/>(d) He is learning cycling / learning to ride bicycle / leaning how to ride (bicycle).<br/><br/>(e) They are putting out the burning house.<br/><br/>(f) They bought a few books at the book fair.