Answer: d. She always leaves early, but the others stay.
Step-by-step explanation: Subject-verb agreement is simply to use singular verbs with singular subjects and plural verbs with plural subjects. In the given sentence we have two subjects, the first one is "she" which is a singular subject, so the correct conjugation of the verb would be "leaves", and the second subject is "the others" which is a plural subject, so the correct conjugation of the verb would be "stay." So the sentence would be "She always leaves early, but the others stay."