催化剂重金属污染产生的后果是（）。
A、催化剂选择性降低
B、催化剂活性下降
C、催化剂稳定性下降
D、抗磨损性下降
参考答案：A, B
Glueear
Viruses can’t be transmitted by (74) and (75) is not a common route for virus infiltration.
A．booting a PC from an infected medium
B．accessing to ROM
C．opening an infected file
D．executing an infected program
