Answer:
1. The bus shuttles <em><u>between</u></em> Delhi and Gurgaon.
2. The children ran <em><u>across</u></em> the bridge.
3. <em><u>Towards</u></em> evening, you can hear the frogs croak.
4. I dug the flowerbeds <em><u>with</u></em> a spade.
5. The mountaineer reached the peak <em><u>with</u></em> great difficulty.
Explanation:
Prepositions are the words that tell us or gives information about the location, place, time, or the relation of the noun or pronoun with the other words in the sentence. In short, they tell us where, when, or how something happens.
The prepositions in the given sentences are underlined as follows-
1. The bus shuttles <u>between</u> Delhi and Gurgaon.
2. The children ran <u>across</u> the bridge.
3. <u>Towards</u> evening, you can hear the frogs croak.
4. I dug the flowerbeds <u>with</u> a spade.
5. The mountaineer reached the peak <u>with</u> great difficulty.