Question

When properly kayaking in the water, your posture should be:

Sitting down with your weight balanced evenly from side to side

Sitting down with your head and shoulders forward and a rounded back for stability

Standing up with one foot slightly in front of the other for balance

Standing up with your feet side by side to keep a high center of gravity

Answer 1

sitting with your weight balanced evenly from side to side,
it cannot be standing as that means that your center of mass is higher now, which would result in instability as centre of mass should be lower, meaning nearer to gravity in order to be more stable
and it cannot be with your head and shoulders forward because that means that you are having your weight distributed unevenly
so i think i would go for the first one
Also, consider asking this in the science section, you would get better results there :)