蛋白质构象容易发生变化，是由于连接氨基酸的（）。
参考答案：肽键键能
---Why are you worried?
--- I’m expecting a call from my daughter. She _______ abroad for three days.
A．has gone to
B．has been to
C．has been in
D．has been
罗茨鼓风机一般应采用（）来调节流量。
