You should suggest where I should go for a holiday, _________? (Add a question tag).
a) should you
b) shouldn’t you
c) would you
d) wouldn’t you

Hint: The given sentence does not contain negation, i.e. the verb is positive. This means that the question tag should be negative. This will help you choose the correct answer.

Complete answer:
 A question tag is a grammatical construction in which a statement that either declarative or imperative is turned into a question by the addition of an interrogative phrase. For example, in the sentence “You’re Shubhi, aren’t you?”, the statement “You’re Shubhi”; is turned into a question by the tag “aren’t you” and a question mark.
However, when the sentence already contains a negative word, the question tag is converted to positive, as double negation is grammatically incorrect. So, if the sentence was “You’re not Shubhi”, the question tag would be “are you?”.
But the sentence in the given question does not contain a negation, which means that the question tag should be negative.

Now, we know which question tag we are looking for. Let’s look at the given options-
a) should you - This option is grammatically correct. It is a positive question tag, it has the correct verb, however, it would not fit into the given question perfectly. This is not the required answer. So, this is an incorrect option.
b) shouldn’t you - This option is grammatically correct. It is not a positive question tag, and it has the correct verb, so it would fit into the given question perfectly. This is the required answer. So, this is the correct option.
c) would you - This option is grammatically correct. It is a positive question tag, it has the incorrect verb, and it would not fit into the given question perfectly. This is not the required answer. So, this is an incorrect option.
d) wouldn’t you - This option is grammatically correct. It is not a positive question tag, but it does not have the correct verb, so it would not fit into the given question perfectly. This is not the required answer. So, this is an incorrect option.

Therefore, the correct option is (b) You should suggest where I should go for a holiday, Shouldn’t you?

Note:
Try to look for certain pointer words. They will help you understand which question tag you are looking for. Then, go through the given options, and choose the most appropriate option accordingly.