Ineed an answer asap

which of the following is a physical change?
question 1 options:

a: toasting a marshmallow

b: tearing a piece of paper in half

c: rusting nails

d: a glowing glow stick

The answer for #3 is c but i don't know why

If the atomic mass of an atom is 34 and the atom contains 13 protons, how many neutrons does the atom contain?

Microtubular fibers that assist in the movement of chromosomes during nuclear division in conjunction with proteins, makes up the small and large organelle pieces that assemble prior to translation three-base nucleotide sequence that can complementarily pair with the functional transcript, allowing a particular material to be brought to a ribosome particular time in the cell cycle when the cell’s systems determine if the cellular conditions are appropriate to continue through the cycle time in the cell’s cycle when proteins are made and organelles are duplicated enzyme that allows proper nucleotide bonding during transcription specific dna sequence which will initiate gene transcription division of the cell’s cytoplasm specific bond that forms between two amino acids when a carboxyl group binds to a amino group three-base sequence that does not code for a particular amino acid a paired organelle which facilitates the formation of movement microtubules time in the cell’s cycle when the microtubular structures exert an equal pressure on the cell’s genetic material