He spent hours _______ with his friend under the bridge.
sit可以是及物动词,用如seat。意为 to cause to be seated : place on or in a seat。所以这种及物动词sit的过去分词,就能表示“使坐下”的动作结束后的状况——坐着。在seating和sat只能二选一的状况下,大家就只能选sat这个过去分词来表示坐着的这种状况。sat的这种使用方法显然不如seated或sitting作状语常用,但语法上是没错误的。所以好题老师的这道题的答案为 sat。