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An atom of lead (Pb) has a mass number of 207. How many neutrons are in the nucleus?

A. 130

B. 125

C. 82

D. 84

Answer Explanation:

We find the number of neutrons as follows

Number of neutrons

= mass number – atomic number

= 207 – 82

= 125 neutrons

Therefore, the Correct Answer is B.

Q #1: A myocardial infarction affects which of the following blood vessels of the heart?

A. Aorta

B. Vena cava

C. Pulmonary

D. Coronary

Answer Explanation

A myocardial infarction refers to heart attack, which result from blockage of blood flowing into the heart.

Blocking is caused by the deposition of fat or cholesterol that forms plaque on the surface of coronary arteries, which supply blood to the heart.
Q #2: Metabolism of proteins Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?

A. Sebum

B. Urea

C. Lysozymes

D. Water

Answer Explanation

Proteins are nitrogen-based compounds, which when broken down release ammonia. Ammonia is a toxic substance to the body, and sebaceous glands coverts it to urea.
Q #3: In a plant in which fuzzy leaves (F) are dominant over smooth leaves (f), which of the following crosses will produce only offspring with smooth leaves?

A. Ff x ff

B. Ff x Ff

C. FF x FF

D. ff x ff

Answer Explanation

Crossing is the breeding of parents to produce an offspring. Given that f is a recessive allele of smooth leaves while F is the dominant allele of fuzzy leaves. Therefore, where there is F crossing with f, the offspring will have fuzzy leaves over smooth one.
Therefore, for an offspring to have smooth leaves, ff and ff must cross to produce an offspring with smooth leaves.

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