这是改错，a,b,c,d,是可能的错误：）

3. It is said that no potential frontier has such fired the imagination or changed the ingenuity of humankind as has space. (a) is said (b) such (c) ingenuity (d) as has 4. Lactose, a sugar present in milk, is one of simple sugars used in food preparations for infants. (a) a (b) present (c) of simple (d) food