Which sentence has an error in subject-verb agreement?
a) the pile of leaves that had been sitting at the end of the road for weeks began to decompose slowly.
b) there are entirely too many ketchup bottles in he refrigerator, and some of them must be thrown away.
c) unlike most runners, charles - - even if parched - - would never drink any water at any point during the run.
d) the man, in the next apartment, as well as the people across the hall, have lived in the building since 1960.

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