The policeman walked towards his jeep.

Explanation:
In this sentence, the word "towards" is used to indicate the direction in which the policeman walked.

- The word "towards" is a preposition that shows movement in the direction of someone or something.
- It is commonly used to indicate movement or motion from one place to another.
- In the given sentence, the word "towards" is followed by the noun "his jeep", indicating that the policeman walked in the direction of his jeep.

Here's how the sentence can be rephrased to understand the meaning more clearly:
- The policeman walked in the direction of his jeep.

Alternative options and their explanations:
a) at - This preposition is used to indicate a specific location or position, but it does not convey the idea of movement towards the jeep.
b) too - This adverb is used to indicate excess or addition, and it does not make sense in the given sentence.
d) by - This preposition is used to show the location of something or someone in relation to another object or person, but it does not convey the idea of movement towards the jeep.

In conclusion, the correct answer is option c) towards, as it accurately conveys the intended meaning of the sentence, indicating the direction of the policeman's movement towards his jeep.