未知题型 This crop has similar qualities to the previous one, _______ both windresistant and adapted to the same type of soil. A) being B) been C) to be D) having been

未知题型 Although they plant trees in this area every year, the tops of some hills are still _______. A) blank B) hollow C) vacant D) bare

未知题型 I have heard both teachers and students _______ well of him. A) to speak B) spoken C) to have spoken D) speak