圆的半径为r，计算圆的面积正确的是：（ ）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 以下那些操作可以新建一个背景？ A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/40aa135f5f0a475f971257bb827504fb.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/9307bb62780f4beb9816a80655aa869f.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/4c22f5c8020040beaa0fe566345b7eb9.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/e66c4f191e944062b31d06d70642aa3f.png" />
- 以下那些操作可以新建一个角色？ A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/be5248f5c01c40febe40711f7db7dbd8.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/bfcfceb7083741d8a0093bd21893a0f2.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/ca41a907d3b648ebb85161bf0477e47d.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/8a75d8860f284339b0d92f7c627b5c9b.png" />
- 以下操作，可以将数据放入列表A的是：（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/be509830d9fa481e937a24d1e2d9ad46.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/56c2e754f3684727b65b6eb649aff2fa.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/a591d719880b457ea72ff0b84b29d4e9.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/deca818437954173af522e786916847f.png" />
- 空心圆轴的外径为D，内径为d, α=d/D。其抗扭截面系数为( )。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/a4529f25a3514c4fb3fb60740f65c915.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/ed201b86c65c4e91be69e526278e5396.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/997a80bcc1dd4cbd9aacbdc8724ccaf9.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/c3e0ca0958684b89bce9d01917a38b5a.png" />
- 关于斜弯曲的主要特征有四种答案，试判断哪一种是正确的。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/42375925fb1245cebbfabe4a5cde4d5a.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/6055f7367a0b466581761cb41cf73e10.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/a028bfcdbbcc4cb592fb6cd9d78b736a.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201907/6abdbfbb54644603b4269b938e091af5.png" />