What type of items are valid for use in the value list of a Case clause?

Attackers circumvent IDSs by implementing techniques such as:

A. Packet fragmentation B. UDP port scans C. NAT translation D. TCP scans

Which statement is false?

a) Function atof returns a double version of its argument. b) If the converted value cannot be represented, the behavior of atoi is undefined. c) When using functions from the general utilities library, its header file must be included. d) Function strtol receives three arguments.