Read the passage carefully and choose the correct answer to each question out of the four alternatives.

Did the earth always____(i)_____ as it does today? No, __(ii)____ its origin about 4.8 billion year ago, our planet has ___(iii)____ a lot of changes. The initial ball of fire ___(iv)___ down and the surface slowly ___(v)__ solid. Today we know that the Earth’s crust is divided into several plates, which move continuously. Entire continents have been displaced and mountains, islands and new seas have been formed or have disappeared.

Q:

Fill in the blank at (iii).

• 1
  undergo
• 2
  undergone
• 3
  undergoes
• 4
  underwent