深松的作用是什么？
参考答案：
深松可以破坏长期犁耕形成的坚硬的犁底层，加深耕作层，改善耕层结构，提高土壤，蓄水抗旱和耐涝能力。
由于（），使龙门刨床侧刀架加工试件垂直度超差。
A.工作台导轨直线度超差
B.机床安装调整变形
C.立柱导轨直线度超差
D.侧刀架导轨精度超差
(1) In the strength of the carrier signal is varied to represent binary 1 or 0.
(2) is a system that can map a name to an address and conversely an address to an name.
(3) is a three-way handshaking authentication protocol that it’s packets are encapsulated in the point-to-point protocol
(4) is an approach that enables an ATM Switch to behave like a LAN switch.
(5) is an guided media which is made of glass or plastic and transmits signals in the form of light.
1（）
A．ASK
B．PSK
C．FSK
D．FDM
