【单选题】Whenever we are in _______, we must never lose _______, but try to think of the way out.
A.
the trouble; our heart
【单选题】We must not lose heart only _____ the difficulty were faced with.
【单选题】Whenever we are in______, we must never lose______, but try to think of the way out.
【单选题】在铰链四杆机构中,如果最短杆与最长杆长度之和大于其余的两杆长之和,那么当取最短杆为机架时,机构为____________。