The sentence requires a preposition to complete the phrase "entered _____ an agreement". The standard and idiomatic phrase in English is "to enter into an agreement", which means to formally start or become involved in an agreement.
Therefore, the correct preposition to signify the formal commencement of the agreement is "into".
A policeman was asked to chase a thief. Before the policeman started the chase, he realised that the thief was 200 metres ahead of him and was running at a speed of 16 km/h. The policeman started the chase at a speed of 20 km/h. How far will the thief run before he is overtaken by the policeman?