Who vs. that
Some people claim that relative clauses which relate to persons should only be introduced by “who” and never by “that,” although the latter option is in fact very common.
According to this logic, the following is WRONG:
“The person that gave me the advice was mistaken.”
It is not wrong. It is just as correct as:
“The person who gave me the advice was mistaken.”
Tracking down the “some people” who/that claim “relative clauses which relate to persons should only be introduced by ‘who’” is difficult. Perhaps because it’s a silly made-up rule.
That said, a fair number of English speakers get irritated when ‘that’ is used for persons, and if the person reading your grant/job application is one of them, consequences may be grave rather than silly. If you don’t know your audience (or you know they are grammar Nazis) and the outcome is important to you, stay on the safe side, otherwise feel free to use whichever you like.
For more on this topic, see: http://www.quickanddirtytips.com/education/grammar/who-versus-that
Of course, never use ‘which’ in place of ‘who’ – “That is that woman which [sic] sits beside me in class” begs for a little ‘discussion’, not unlike here:
Jason Blake and Monika Kavalir