both, whether, neither, or, nor, but ____ by accident ____ by d

both, whether, neither, or, nor, but
____ by accident ____ by design, he arrived too late for the appointment.
【正确答案】：Whetheror
【题目解析】：【考点点击】本题考查whetheror的用法。【要点透析】作“是…还是…”理解时, whether表示一种选择,其后可以跟介词短语或不定式短语。