I know you would have to prolong your tour; but still I advise you to complete this job also.

Answer: Option B

Prolong : extend the duration of.
Obstruct : block (an opening, path, road, etc.); be or get in the way of.
Curtail : reduce in extent or quantity; impose a restriction on.
Hinder : make it difficult for (someone) to do something or for (something) to happen.
Restrain : prevent (someone or something) from doing something; keep under control or within limits.

Antonym of Prolong is Curtail