In the following passage some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each number.
Antarctica is perhaps the one place on Earth no one would have expected (1)______ canyons. And yet, scientists were surprised to (2)______ deep crevices that run for hundreds of kilometres. (3)______ they are not visible at the snowy surface, (4)______ trenches cut deep into Antarctica. The biggest (5)______ canyon is over 350 km long. It’s called ‘Foundation Trough’. (6)______ canyons are not as long, but they are (7)______ too. These canyons were found with the help of radars (8)______ scanning the wide expanse of the frozen continent. (9)______ are incredibly important because they help control (10)______ flow of the ice.
Select the most appropriate option to fill in the blank No. 2. 

Options

A. invent
B. search
C. explore
D. discover

Answer

D