What has a ring but no finger?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

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?”

Which is faster, Heat or Cold ? Explain.

What breaks yet never falls, and what falls yet never breaks?

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

Can you find the 09 errors in the picture below?

John was piloting a plane behind a car but was never able to overtake it. Why?

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?