Well, using Math to see how far the Moon is from the Earth could be hard. Also, he saw that the Moon is moving in a "circle" instead of flying off, so the Earth did have a pull on the Moon so that it didn't fly away. Newton had to use Math in order to be able to identify what it's now called gravity. There's a lot that the Moon has to offer, there were no computers back then, so there's was no calculator and everything had to be done by hand.
The phrase that best describe the word "energy" is letter "C. the ability to do work". The unit most commonly used to express energy is Joules (J) which is also derived from the equation of work which is the product of force and the distance that a body moves parallel to the force applied.
DNA replication needs to occur because existing cells divide to produce new cells. Each cell needs a full instruction manual to operate properly. So the DNA needs to be copied before cell division so that each new cell receives a full set of instructions!
Infectious agents are those that corrupt and prey on an organism or a host. This is sometimes called parasitism when a foreign organism consumes a host by preying on its nutrients and food. Hence, we are uncertain in Anna's case because there is no clear description of her symptoms.
