下列关于核酸的叙述，正确的是（ )
A：核酸由C、H、O、N四种元素
B：在真核细胞内，核酸只存在于细胞核内
C：组成核酸的基本单位有8种
D：除病毒外，一切生物都含有核酸
— But you know what they say—________ makes the heart grow fonder.
— How do you like the regulations of our school?
— The regulations are strict with the students and they require that students _______ at least 90% of the lectures.
下列关于责任的说法，你认为正确的是（ ）
