The forekonwledge of Christ that he was sitting under the fig tree.

 Christ also promised Nathenael to see & here much more

Jesus could not answer them because on the account of his words he could be convicted. His words could be used against him

Again even answering them he could not be released. They had made up their mind on onvicting Him

 He also knew his destiny. To die on the cross and  this was the time