Correct Answer: B

The direction of the electric field is the same as the direction of the force on a positive test charge. Moving a negative charge in the direction of the electric field requires an external force to oppose the electric field. This would increase the electron's potential energy.

Correct Answer: A

Sound travels much faster through helium than through air. Generally, the speed of sound can be calculated by speed = (k ?P / ), where k is the index of specific heats, P is pressure and is density. Since helium has a much lower density, it would have a higher speed.

Correct Answer: B

This question can be solved in numerous ways. If 1 gallon has 20% apple juice, it means apple juice consists of 0.2 gallons. If the 2 gallon has 30% apple juice, it means apple juice consists of 0.6 gallons. Thus, there are a total of 0.8 gallons of apple juice in the mixture of the total 3 gallons.

Find the percentage: (0.8 gallons of apple juice / 3 total gallons) × 100 = ~27%

Correct Answer: B

Multiply $120 by 24 months (a full two years) to get $2880. Add the thousand dollars for the down payment to get $3880. Find the difference between the entire amount all at once ($2600) and the amount paid in the plan ($3880). To find the difference, you subtract. The difference shows that $1280 more is paid with the installment plan.

Correct Answer: D

x / 3 + 4 = 7, x / 3 = 3, x = 9.

Correct Answer: C

An animal cell has neither chloroplast nor vacuole, thus B and D can be eliminated. In an animal cell, the nucleus is indeed the largest organelle (in relation to diameter).

Correct Answer: D

If there are 46 homologous chromosomes present, it means there is a total of 92 chromosomes. 46 come from the father, 46 from the mother. Thus with 92 chromosomes, there is a total of 184 chromatids.

Correct Answer: E

The endosymbiotic theory explains the mitochondria and chloroplasts found in eukaryotic cells (the latter in plant cells specifically). A bacteria was engulfed (but not digested) by a eukaryotic cell, forming a symbiotic relationship that later lead to the double membrane contained organelles.

Correct Answer: C

All the other hormones in the answer choices are hormones of the anterior pituitary.

Correct Answer: E

Keto-enol tautomerism is the equilibrium between a keto form and an enol form (alcohol) of a chemical. In this scenario, both answer choices B and C are applicable keto-enol tautomers, although the frequency of one form compared to another may be shifted.