Question

Choose the best option to complete each sentence.
Engineers have now made ships that can sail ________ the sea and fly _____ the air.
a. on, on
b. on, in
c. in, on
d. at, off

Answer 1

Hint: We have to choose the best prepositions to complete the sentence. For anything which has a surface, we use “on”. If there is no surface, we use “in”.

Complete answer: As we all know, a preposition is a linking word. It helps to signify the position of the object.
Let us look at the sentence to understand which prepositions to use. The sea has a surface. Just like a cat sits on a mat which has a surface, a ship shall also sail on the sea. Therefore, the first option will be ‘on’. In the second blank, we have to determine the preposition to use with respect to objects in air. Air has no surface since it is gaseous. Thus, any object is always ‘in’ air. The second answer will be ‘in’. The answers ‘on’ and ‘in’ are given in option b. Therefore, the correct answer is option b.
Let us consider some other examples.
She kept the cup on the table. A table has a surface. Similarly, she left her clothes on the bed. She was standing on the steps. It is common knowledge that a bed and steps have a surface too.
Now let us see some sentences where we can use ‘in’. If there is something through which something can pass, we can use the preposition ‘in’. The ball is in the air. The ball can easily pass through the air and thus we use the preposition ‘in’.
Similarly, the cat sat in the box. She left her phone in the bathroom. She travelled in a car. As we can see, the objects box, bathroom and car, all have depth in them. There is a certain amount of space in all of these objects which allows something to be in them. Thus, we use the preposition in.

Note: When there are questions which have two answers, make sure the option you are choosing has both of its answers as correct. If only the first answer is correct and the second answer is wrong, the whole option will be wrong.