单项选择题 A hotel is like a self-contained community providing guests with all the services they can expect in their own home and community（）

单项选择题 If the engine is to be shut down for a long time, we recommend the following measures for the engine to avoid corrosion（）

单项选择题 As is known to all, trade and specialization go hand in hand and enable each of us to have more products to use（）