luó / shuān / shàng / shǎo / le / yí / ge / diàn / quān / suǒ / yǐ / xū / yào / mǎ / shàng / gēng / huàn螺栓上少了一个垫圈,所以需要马上更换。A washer is missing from the bolt, so it needs to be replaced immediately.