目前使用较普遍的发光二极管无管座，全部用透明的环氧树脂封装，这类管子上电极引线较长的是（）。
A、正极
B、负极
C、基级
D、发射极
参考答案：A
侵犯商标权的表现形式主要有哪些
Most computer systems are (16) to two different groups of attacks: Insider attacks and outsider attacks. A system that is known to be (17) to an outsider attack by preventing. (18) from outside can still be vulnerable to the insider attacks accomplished by abusive usage of (19) users. Detecting such abusive usage as well as attacks by outsides not only provides information on damage assessment, but also helps to prevent future attacks. These attacks are usually (20) by tools referred to as Intrusion Detection Systems.
A．visit
B．access
C．I/O
D．read/write
