1. How many bones are there in the adult human skeleton?

A. 126
B. 206
C. 300
D. 525

Correct answer: D

Rationale: The correct answer is D: 525. The adult human skeleton consists of 206 bones. However, when accounting for individual bones, many of them are paired (like the ribs and vertebrae), bringing the total count to 206 individual bones but 525 in total when considering pairs. This includes bones in the skull, spine, ribs, arms, hands, pelvis, legs, and feet. So, while there are 206 individual bones, the total number of bones in the adult human skeleton is 525 when considering pairs.

2. The athlete ran the race in record time. Which word is the present participle of the verb "run"?

A. ran
B. runs
C. running
D. runner

Correct answer: C

Rationale: The present participle form of a verb describes an ongoing action.

3. Which hormone is responsible for regulating sleep-wake cycles and is influenced by light exposure?

A. Melatonin
B. Cortisol
C. Estrogen
D. Glucagon

Correct answer: A

Rationale: The correct answer is A: Melatonin. Melatonin is a hormone produced by the pineal gland in the brain and plays a crucial role in regulating the sleep-wake cycle, also known as the circadian rhythm. Melatonin levels typically rise in the evening in response to darkness and help signal to the body that it's time to sleep. Exposure to light, especially blue light, can inhibit the production of melatonin, making us more alert and awake. Cortisol (option B) is a stress hormone that helps regulate metabolism and immune response. Estrogen (option C) is a female sex hormone, and glucagon (option D) is a hormone that increases blood sugar levels. Therefore, the hormone responsible for regulating sleep-wake cycles and influenced by light exposure is melatonin.

4. Which sentence uses parentheses correctly?

A. The suspect was seen driving a red car (a witness reported).
B. The movie (released in 2022) received critical acclaim.
C. The restaurant offers a variety of dishes (including vegetarian options).
D. All participants (must register by Friday) will receive a free gift.

Correct answer: B

Rationale: Parentheses are used for non-essential information that clarifies or adds detail. Option (a) is unnecessary and disrupts the flow of the sentence.

5. What is the primary difference between ionic and metallic bonding?

A. Ionic bonds involve electron sharing, while metallic bonds involve electron transfer.
B. Ionic bonds are weak and directional, while metallic bonds are strong and non-directional.
C. Ionic bonds exist between metals and non-metals, while metallic bonds exist only between metals.
D. Ionic bonds form discrete molecules, while metallic bonds form extended structures.

Correct answer: B

Rationale: Ionic bonds form discrete molecules, while metallic bonds form extended structures. Ionic bonds involve complete electron transfer between specific atoms, resulting in discrete molecules. Metallic bonds involve a "sea" of delocalized electrons shared across all metal atoms, leading to strong, non-directional bonding throughout the entire material.

6. What is the medical term for heartburn, a burning sensation in the chest caused by stomach acid?

A. Dysphagia
B. Gastroesophageal reflux disease (GERD)
C. Peptic ulcer
D. Ulcerative colitis

Correct answer: B

Rationale: Rationale: A) Dysphagia refers to difficulty swallowing and is not specifically related to heartburn. B) Gastroesophageal reflux disease (GERD) is the medical term for heartburn, which is a burning sensation in the chest caused by stomach acid flowing back up into the esophagus. C) Peptic ulcer is a sore that develops on the lining of the stomach, small intestine, or esophagus, and it can cause symptoms such as abdominal pain, not specifically heartburn. D) Ulcerative colitis is a type of inflammatory bowel disease that affects the colon and rectum, and it does not typically cause heartburn.