ponder       
verb [ I or T ]  formal uk/ˈpɒn.dər/ us/ˈpɑːn.dɚ/
C2 沉思,默想,考虑
to think carefully about something, especially for a noticeable length of time
  She sat back for a minute to ponder her next move in the game. 她在椅背上靠了一会儿,思考下一步棋该怎么走。 
 Synonyms: contemplatemeditatemuse reflectruminatespeculate