Answer: D. 
Explanation:
The energy 
of an electromagmetic wave is given by:
Where:
is the Planck constant
is the speed of light in vacuum
Then 
is the wavelength
Solving:
Answer:
2 m
Explanation:
Work = force × distance
500 J = 250 N × d
d = 2 m
She moved the couch 2 meters.
Answer:
Elements in a period have wide range of chemical properties.
Explanation:
- Period is the row of chemical elements's arrangement in the periodic table. It is numbered from 1 to 7.
- In period as we move towards right the atomic number of element constantly increases along with the change in chemical properties.
- As we move from left towards right in period, the valence electron number regularly increases in every element.
- This valence electron differs the reactivity of the elements.
C. Mechanical, because temperature can cause solid objects to expand and contract, causing rocks to split apart.
