在电子显微镜下观察，有时看到内质网包裹的线粒体。
参考答案：对
The professor requested that all the students ________ the reports at once.
A．would hand in
B．handed in
C．hand in
D．handing in
HLA-B27抗体常出现在
A．强直性脊柱炎B．类风湿性关节炎C．骨关节病D．皮肌炎E．系统性红斑狼疮
