What does this below rebus puzzle mean?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

Why is a river so rich ?

How many triangles are there in the picture below?

Two guards were guarding the camp.Guard-1 was looking towards the south to make sure no threat is coming from the road.Guard-2 was looking at the north to make sure no threat is coming from the top. Suddenly Guard-1 ask the Guard-2 why he is smiling?How Guard-1 knows that Guard-2 is smiling?

Can you count the number of triangles in the given figure?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

I look at you, you look at me I raise my right, you raise your left. What am I?

Bay of Bengal is in which state?

To attend world science seminar, A famous chemist from Mexico visit
London. In the lab, the scientist was killed and his six assistants were under suspicion of killing the chemist.
Name of six assistants: Austin, Wayne, Dege, Oscaru, Lingard, and Rojo.
He left a note "76-20-44 79-16-22-7"

A local detective Jack was called to solve the case,

After reading the note, Jack instantly asked the police to arrest the murderers.

Who are the murderers?