1. Dandruff is caused by

A. Excessive sebum production (This can contribute to oily dandruff)
B. Bacterial infection (This can cause scalp folliculitis, not dandruff)
C. Overgrowth of a specific type of fungus on the scalp
D. Lack of proper skin hydration

Correct answer: C

Rationale: Dandruff is primarily caused by an overgrowth of a specific type of fungus called Malassezia on the scalp. This fungus feeds on the natural oils produced by the hair follicles, leading to an inflammatory response in some individuals, resulting in flaking and itching. Excessive sebum production can contribute to oily dandruff by providing more food for the fungus. Bacterial infections, such as scalp folliculitis, can cause symptoms similar to dandruff but are not the primary cause. Lack of proper skin hydration can contribute to dry scalp conditions but is not the main cause of dandruff.

2. What is the functional group present in esters?

A. Hydroxyl
B. Carbonyl
C. Ester
D. Amine

Correct answer: C

Rationale: Esters have the functional group -COO-, representing a carbonyl group bonded to an oxygen atom. The other choices are associated with different functional groups.

3. Which technology allows scientists to directly edit the human genome?

A. Polymerase Chain Reaction (PCR)
B. Gel electrophoresis
C. DNA sequencing
D. CRISPR-Cas9

Correct answer: D

Rationale: Rationale: A) Polymerase Chain Reaction (PCR) is a technique used to amplify a specific segment of DNA through repeated cycles of heating and cooling. PCR is not used for directly editing the human genome. B) Gel electrophoresis is a technique used to separate DNA fragments based on size. It is not used for directly editing the human genome. C) DNA sequencing is a method used to determine the precise order of nucleotides in a DNA molecule. While DNA sequencing is important for understanding genetic information, it is not used for directly editing the human genome. D) CRISPR-Cas9 is a technology that allows scientists to make precise changes to the DNA of living organisms, including the human genome. CRISPR-Cas9 works by guiding the Cas9 enzyme to a specific location in the genome where it can make targeted cuts or edits. This technology has revolutionized genetic research and has the potential for applications

4. What property of a wave remains unchanged when it passes from one medium to another with the same speed?

A. Frequency
B. Wavelength
C. Amplitude
D. Speed

Correct answer: d

Rationale: The speed of a wave remains constant when passing from one medium to another with the same speed.

5. Glands that release hormones directly into the bloodstream without ducts are called:

A. Exocrine glands
B. Endocrine glands
C. Apocrine glands
D. Merocrine glands

Correct answer: B

Rationale: The correct answer is B: Endocrine glands. Endocrine glands are specialized glands that release hormones directly into the bloodstream, which then travel to target organs or tissues to regulate various physiological processes. Unlike exocrine glands (choice A), which secrete their products through ducts to specific locations, endocrine glands secrete hormones into the blood for more widespread and systemic effects. Apocrine glands (choice C) release a portion of their cell contents along with the secretions, while merocrine glands (choice D) release their products through exocytosis without any loss of cell material. Therefore, in this case, endocrine glands best describe the glands that release hormones directly into the bloodstream without ducts.

6. What is the atomic number of an element?

A. The number of protons in an atom's nucleus.
B. The number of neutrons in an atom's nucleus.
C. The number of electrons in an atom's valence shell.
D. The number of isotopes of an element.

Correct answer: B

Rationale: The atomic number of an element is a fundamental property that defines the identity of an element. It is the number of protons in the nucleus of an atom. The number of protons determines the element's position in the periodic table and its chemical properties.