I came across this SAT Question of the Day:
Unbelievable as it may seem, many individuals that fought in the American Revolution were still alive in 1839, the year the world was introduced to photography. (choose the error - the 'answer' is in bold)
It noted that the reason "that fought" is wrong is that 'The relative pronoun “that” may not be used to refer to people (“individuals”) and should be replaced with the relative pronoun “who.”'
I had thought that the word "that" could refer to both people and objects (while which was reserved for objects and who reserved for people). Am I wrong?