Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

Sherlock breaks into a crime scene. The victim is the owner who is slumped dead on a chair and have a bullet hole in his head. A gun lies on the floor and a cassette recorder is found on the table. On pressing the play button, Sherlock hears the message 'I have committed sins in my life and now I offer my soul to the great Lord' and followed a gunshot Sherlock smiles and informed the police that's its a murder.

Why did he think so?

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

I am the fastest animal but cannot climb the tree. What am I?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

The captain of a ship is telling you an interesting story and then poses a question. He says, “I have travelled the oceans far and wide. One time, two of my sailors were standing on opposite sides of the ship. One was looking west and the other one east. And at the same time, they could see each other clearly. Can you tell me how that was possible?”

How can you make number one disappear by adding something to it?

Name a key which is hardest to turn.

What does this rebus photo means?