Choose the sentence that uses the preposition incorrectly:

The correct answer is Option (3) → The kite is flying on the sky.

In and on for place:

• On is used for something resting on a surface: on the table, on the wall, on the floor.
• In is used for something inside a space or an area: in the room, in the water, in the sky.
• The sky is a space, not a surface, so a kite flies in the sky: "The kite is flying in the sky." "On the sky" is the incorrect use.
  Example: Hundreds of stars twinkled in the sky.

Why the Other Options are Incorrect?

Option 1: Read the poem on page 50. — Incorrect. Correct use: we say on page 50, since the words are on the surface of the page.

Option 2: I live on street 10. — Incorrect. Correct use: on is used with the name of a street or road (on Park Street, on MG Road).

Option 4: Put on your new clothes. — Incorrect. Correct use: put on is a phrasal verb meaning to wear.
Example: Put on a sweater; it is cold outside.

Contrast: on a surface (on the table, on page 50); in a space (in the room, in the sky).