李大爷是糖尿病患者，你给他提供的治疗方案是注射[ ]
A．生长素
B．甲状腺素
C．胰岛素
D．肾上腺素
答案：C
He is always ready to help others. That's one of his ________ .
A．strengths
B．powers
C．abilities
D．benefits
试叙述四种青贮方式的特点及应用场合。
