Choose the word(s) which can correctly replace the word(s) printed in italic in the sentence without changing the meaning of it.
Your master will like you if you are diligent.
a. Conscientious
b. Obedient
c. Meticulous
d. Hard-working

Hint: A diligent person is someone who puts in a lot of effort into his work and is very sincere about it. Since we cannot change the meaning of the word, we have to select a word which means similar to the word ‘diligent’.

Complete answer:
Some more examples will make it easy to understand.
Let us take the word ‘permanent’. Something which is permanent is something which is long-lasting; which cannot be easily removed. For example, I got offered a permanent position in the company. This means that my position is unlikely to change. A word similar to permanent is everlasting. Everlasting things last forever. The quality of some wooden furniture is so good that it is everlasting. Thus, the words permanent and everlasting are similar to each other.
Let us take another word, for example, ‘stop’. To stop something means to end something. She stopped the blood flow by wrapping a cloth over it. A word similar to the word stop is end. To end something is to stop it or to finish it. The exams ended on Tuesday. Thus, the words stop and end are similar words.
Therefore, from the given options, we can see that option d is ‘hard-working’. The other meaning of diligent is hard-working. Thus, we can substitute the meaning of diligent with the word ‘hard-working’ without changing the meaning of the sentence. Hence, the correct option is option d.

Note: From the options given, it is easy to get confused between options b, c and d. However, it is to be noted that diligent means to be hard-working. Being meticulous and obedient are like a part of being diligent.