标题: prep12 SC09 [打印本页] 作者: turbidtear 时间: 2015-5-31 19:46 标题: prep12 SC09 Roughly twice each century the planet Venus passes between the Earth and the Sun, an occasion known as a transit of Venus, during which it makes the outline of the planet visible in stark relief.
B.during which the outline of the planet becomes
答案是上面这个，我想问duiring which前面要有表示一段时间的先行词吧？还是说根据句意是一段时间，就可以用？