ponder

1. V-T/V-I If you ponder something, you think about it carefully. 仔细思考

I found myself constantly pondering the question: "How could anyone do these things?"

我发现自己不停地思索着这个问题：“怎么会有人做出这些事情？”

He pondered over the difficulties involved. 他仔细思考了有关的种种困难。