ponder 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.