When a contractor is ready to begin construction of asuperhighway, he makes a preliminary study of the drawings andblueprints supplied by the engineers. He gains mental picture. of the whole jobbefore he begins actual construction.
A.preparatoryB.extensiveC.scientificD.necessary在线课程A
解析：
从整句话的意思来看，preliminary study是发生在actual construction之前，所以它的意思应是初级的，预备的，所以答案应为A