Answer:
B. Below.
C. On.
B. Across.
Explanation:
Prepositions are the parts of speech which provide the location/position of the thing talked about. They are used to connect nouns, pronouns or even phrases with the other people or give the time or location/ place of the other people.
1. <em>The life jackets are stored </em><u><em>below</em></u><em> the deck.</em>
The preposition here is BELOW which shows the position of the life jackets. It gives the location of the life jackets, making it easy for their easy finding.
2. <em>I hope to visit my Grandmother </em><u><em>on </em></u><em>Wednesday.</em>
Here, the preposition is ON for it tells the time/exact day of the speaker's plan to visit his/ her grandmother. It provides the extended detail for the visit, giving a specific detail.
3.<em> If you walk </em><u><em>across</em></u><em> the bridge, you will see two windmills.</em>
Lastly, the preposition in this sentence is ACROSS which suggest/ shows the very act of moving. It is usually followed by a noun, in this case "the bridge".