Because log-on procedures may be cumbersome and tedious, users often store log-on sequences in their personal computers and invoke them when they want to use mainframe facilities. a risk of this practice is that
(a) backup procedures for data files would not be as effective.
(b) users with inadequate training would make more mistakes.
(c) anyone with access to the personal computers could log on to the mainframe.
(d) personal computers become much more likely to be physically stolen.

(C) Anyone with access to the personal computers could log on to the mainframe.

Explanation:

It is no doubt that log on procedures are cumbersome so what most users do is that they store log on sequences in their computer so that they could use the main frame facilities whenever they access it the second time.

Here we have to identify the associated risk with this approach.

This process could lead to access of the computer system to users and thereby making all the data available in the system vulnerable. So option C is correct.

option (A) is incorrect as the back up option who also be affected when the system is accessible to anyone.

option (B) is incorrect because it has nothing to do anything with training of the personnel.

option (D) is incorrect because it one has nothing to do with the physical system what vulnerable reside is inside the system.