He是人称代词,接suggestion名词怎么都别扭啊,应该是his吧?
His suggestion 是先行词,that后面跟的we set off now是同位语,解释suggestion的内容.
而这个句子的主句是His suggestion has been accepted.他的建议被接纳了.
而这个建议就是we set off now.
所以整个句子的意思是：His suggestion（ that we set off now）has been accepted.他的建议——“我们现在出发”被接纳了.