Select the most appropriate option to fill in the blank.

One has to be persistent in studies if he/she wants to get his/her dream job. Success will remain unattainable if one studies _______ .

by fits and starts

The correct option to fill in the blank is by fits and starts.

The phrase "by fits and starts" means in a way that is not continuous or regular. This is the most appropriate option in this context because it conveys the idea that someone who studies by fits and starts is not being persistent and is not likely to achieve their goals.

The other options are incorrect.

• Root and branch means completely and thoroughly. It does not make sense to say that someone who studies root and branch is not likely to achieve their goals.
• The three R's refers to reading, writing, and arithmetic. It does not make sense to say that someone who studies the three R's is not likely to achieve their goals.
• In ups and downs means with some successes and some failures. It is a more general phrase than "by fits and starts", and it does not specifically convey the idea of lack of persistence.