WOULD : when to use ?

As a non-native, I often used to get confused with the usage of the word - would , so I decided to demystify its usage for everyone like me through the following article. I spent some time exploring the usage of would and I am sharing what I understood.

Readers press kudos or advise change through comments.

Usage of would be divided into the following 4 basic categories.

1. Past would :
To describe repetitive habit or action, which has stopped in the past. would = used to - interchangeable in most of the cases.
She used to bring me gifts when she came to my house. (now she does not)
She would bring me gifts when she came to my house. (now she does not)
You would always take your surfboard when you went to the beach. (now you do not)
would you always take your surfboard when you went to the beach?

Note : Would can not describe a past state.
She would be shy, but now she is outgoing. (wrong) - shy is a state (adjective) not a repetitive habit or action.
She used to be shy, but now she is outgoing. (Correct)
She was shy, but now she is outgoing. (Correct)

2. Conditional would:
In if.. then clause - to describe hypothetical subjunctive case. (In Hindi Hypothetical Subjunctive : agar aisa hota to, kya? )

Present: If I were a rich man, I would buy a Mercedes Benz.

Future: I will not shift my furniture tomorrow. If I had, then I would buy you lunch.
I have changed my plan, and now I will not shift my furniture tomorrow, and I am just presenting an unreal situation by saying "I would buy you lunch".

Refer to this link to understand the future hypothetical subjunctive cases mentioned above. https://www.englishpage.com/conditional/ ... ional.html

Past: If you had learned Chinese, then you would have received interview calls from China.

3. Future in the past:
"I knew"(past)-->---(would)---<--present-->--- future.
I knew you would help me.
I knew he was going to go to the party. (PLAN) -- "was/were going to" works like would but they are not interchangeable.
I knew Julia would make dinner. (VOLUNTARILY)

4. To express desire or preference:
I would like to come to your party.
Would you like to sit here?

These are 4 basic categories from the GMAT perspective one must be aware of. Refer to the following question to bolster your understanding.

A recent study on Lyme Disease suggests that people who are bitten by ticks, especially by the lone star tick, develop a severe allergy to the meat that scientists believe to be turning into an epidemic

a.to be
b.would be
c.is
d.it is
e.it would be

Test choice B.
Try to categorize the requirement of would under 4 categories, which I presented above.
Category 2. if..then.. conditional (No) cause and effect not expressed.
Category 3. Future in the past (No) Past tense is not used at all in this sentence.
Category 1. Past repetitive action (No) because we are not talking about any repetitive habit or action of the past, which stopped in the past.
Category 4. Desire (No)

Definitely choice B is not fitting into this sentence. The rest of the choices except C are incorrect for other reasons.

I hope this article helps clear some of your doubts regarding the usage of would. Please suggest if any correction is required or share SC questions on this thread related to the usage of would so that we all can refine our understanding further.