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general::
verb ADV. carefully, deeply, hard | (for) a moment She pondered for a moment before replying. VERB + PONDER leave sb to He walked out of the room, leaving me to ponder what he had just said. | be forced to PREP. about This was something I had been pondering about for some time. | on I walked up the stairs, pondering on her reaction to my news. | over I pondered hard over the reply to his letter.
Oxford Collocations Dictionary