Answer: B
Explanation: A closed system can be defined as a system that does not allow for an exchange of matter with its surroundings.
An estuary where fresh water and ocean water mix is not a good example of a closed system because fresh water and ocean water mix out in the open and matter is exchanged.
A living single-called organism such as phytoplankton does not constitute as a closed system because in order for the phytoplankton to be considered alive it needs to interact with its surroundings i.e light from the sun so photosynthesis (converting light energy into chemical energy to be used by organism) can occur. This also happens out in the open
A river that flows into the ocean does not fit into the closed system definition. This is because a river that flows into the ocean allows for itself (matter) to mix with that of the ocean in an open space (rivermouth).
Therefore option B is the answer because it fits the definition. A chemical reaction within the deep ocean organisms that allows them to glow happens within (inside) the organism, making this system closed, hence there is no exchange of matter with surroundings.
A solar eclipse occurs<span> when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. </span>A solar eclipse<span> can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth's surface.</span>
Deadlifts help develop the lower back and quadriceps. The first option is correct.
<u>N</u><u><em>atural selection acts on existing heritable variation</em></u>
Answer: Option C
<u>Explanation:</u>
Natural selection is a process that occurs in nature as a key to evolution. It also goes hand with the survival of the fittest. Nature always selects the best trait to survive or get accustomed to the surrounding by undergoing modifications.
It acts on the genotype of the existing generation and causes variation in the future generation. So the population over generations get to have acquired the variations in their body, structure so that it is adaptable to the surrounding.
