economic conditions improved -->the adoption of the policy of free trade-- >rise in the prosperity of England 那么直接的原因是经济环境好了，导致了英国的繁荣。（一件事物发生好转，导致另一件 事物导致好转） A：An exhaustive search of the marshes last year revealed no sign of marsh hawks, so it can be assumed that a similar search this year would reveal equally little sign of that kind of bird. 先发生的事物没有向好的地方发展，后发生的也没有变化 B：Building a circular bypass around Plainfield probably helped the flow of local traffic in the town center, since a circular bypass road generally cuts a city’s through traffic markedly. 前者，路切断城市的交通，P附近的建筑可以帮助交通人流。 这个也没有体现好的地方的发展（improve） C:Before the banks raised their interest rates, people on average incomes could almost afford a mortgage for an amount twice their salary. Hence the rate increase has now put mortgages beyond their reach. 都两倍了，当然不是好的发展 D：Since the improvement in the company’s profitability began to occur after the vice president’s new morale-building program was put in place, that program can be credited with the improved result 公司利润提高，导致了工程提高了进度。前者的好的地方的发展，导致后者好的地方的发展 E：The extinction of the dinosaurs was brought about by an asteroid colliding with Earth, so their extinction could not have come before the collision 这个也无关与题目的总结 | 
