To me, they all look good, with the except of these two:
- His wife is at college.
- His wife is at the college. <location>
- His wife is in college. <she's a student>
- His wife is in the college. <doing something>
- Our secretary is sending a fax at the office now.
- Our secretary is at the office sending a fax now.
- Our secretary is sending a fax from the office.
Student or Learner