Which of the following demonstrates proper form for a lunge?

Which of the following demonstrates proper form for a lunge

1. Back knee touches the ground.

2. Front knee is over the front foot.

3. Knees are kept straight.

4. Knees extend past the toes.

one time i was looking at my neighbors screen door to see if the door was open i was squinting like a fool for 10 minutes before realizing he was starring back i then died from embarrassment and am now typing this from the ghost world