"SO" and "BECAUSE" both are conjunctions, but if we talk about its use is completely different. Let's start with "So"
SO: So is used as a conjunction as well as an adverb.
As an adverb: "So" as an adverb means "at an extreme degree, level or extent". Clear it further with examples.
Example:
1. Ahmed drives the bus so fast. ( it means to an extreme speed)
2. Haniya was looking so pretty in the School Annual Function. (Here "so" also intensifies the sentence).
As a Conjunction: "So" as a conjunction is used when someone does an action for a reason.
Structure.
REASON+SO, ACTION
Example:
1. Jiya was tired so she took a rest. (Jiya was tired and for that reason, she took rest).
2. I was feeling cold so I closed the windows. (I was feeling cold and for that reason, I closed the windows).
Because: As a conjunction, it is used when someone has a reason to do an action.
Structure.
ACTION+BECAUSE, REASON
1. I had headache ______ I took tablet
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2. We had a confusion in a Mathematics Problem ______ We went to Sir Shoaib
3. Mam called me ________ she needed my Physics book
4. I am going early today, ___________ I will meet Mehmud.
5. I was hungry _______ I ate an apple.
6. I need some money ________ I have to buy an advanced Computer.
7. I wanted to talk to Mr.Hussain _____ I called him on his Whatsapp number
8.I used Mobile _____ I wanted to listen to songs.
9. please cut the cake _____ we can start the dinner
10. Wahhab went to Moshin _____ he needed to get some important notes from him