Which of the following is not one of the four main criteria that scientists use to determine if an idea is scientific?
- the idea is observable.
- the idea is always true.
- the idea is testable.
- the idea is repeatable.

2. how is heavy water different from normal water

Which of the following has wavelength longer than the wavelength of viable light? a) x rays b) gamma rays c) radios waves d) ultraviolet waves

Question 3(multiple choice worth 4 points) (04.04 lc) what does it mean when an element is reduced? it empties a valance shell, reducing its atomic radius. it gains electrons, reducing its overall charge. it increases electronegativity, reducing its ability to bond. it loses electrons, reducing its electron number.