Plsss!! Which of the following equations is balanced?

Question 3 options:

1) 2H2 + O2 → 4H2O

2) 4Na + O2 → 2Na2O

3) Fe2O3 + H2 → 2Fe + 3H2O

4) CH4 + O2 → CO2 + H2O

What royal scientist used the 29th day of frozen vapor to encounter elements for mastering new culinary creations?

Two people each hold the end of a rope and create waves by moving their arms up and down. this wave is best classified as a transverse wave because a) both the rope particles and the wave are moving in the same direction. b) the wave is moving up and down as the particles of the rope move horizontally. c) the wave is moving horizontally as the particles of the rope move up and down. eliminate d) the wave is moving in a parallel direction with the motion of the person's arms.

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.