The radii of curvature of the faces of a double

Find the appropriate word.

From the following select the appropriate word to replace number (50) in the above passage. 

Fill in the blank with the most appropriate word.

Choose the appropriate word to fill the blank.

Select the most appropriate option to fill in the blank No. 3.

Find the appropriate word for 21.

Find the appropriate word.

From the following select the appropriate word to replace number (48) in the above passage. 

What did the kids learn, after swimming in the sea and getting their colour changed?

Find the appropriate word.