Which one is a sign of puberty in girls?

Energy in an ecosystem originates from the sun. Producers (like plants) convert solar energy into chemical energy. Primary consumers eat producers, secondary consumers eat primary consumers, and so on.

• A: sun → secondary consumer → primary consumer → producer (Incorrect order)
• B: secondary consumer → tertiary consumer → producer → sun (Incorrect order)
• C: producer → primary consumer → tertiary consumer → sun (Incorrect order, sun is the initial source)
• D: sun → producer → primary consumer → secondary consumer (This sequence correctly shows the energy transfer from the sun to producers, then to primary consumers, and finally to secondary consumers.)

The final answer is $\boxed{\text{D}}$

10)

When muscles work intensely and oxygen supply is insufficient, they switch to anaerobic respiration. This process breaks down glucose without oxygen.

The main product of anaerobic respiration in human muscles is lactic acid, which accumulates and causes muscle fatigue.

• A: oxygen (Used in aerobic respiration, not a product of anaerobic)
• B: ethanol (Product of anaerobic respiration in yeast, not human muscles)
• C: lactic acid (Correct, builds up in muscles during anaerobic respiration)
• D: carbon dioxide (Produced in aerobic respiration, not the primary product of anaerobic respiration in muscles)

The final answer is $\boxed{\text{C}}$

11)

Tobacco smoking is a major risk factor for various diseases, particularly affecting the respiratory and cardiovascular systems.

• A: liver cirrhosis (Primarily caused by chronic alcohol abuse or hepatitis)
• B: emphysema (Correct, a chronic lung disease characterized by damage to the air sacs, strongly linked to smoking)
• C: hallucinations (Not a direct or common effect of tobacco smoking)
• D: damaged muscles (Not a primary direct effect of tobacco smoking)

The final answer is $\boxed{\text{B}}$

12)

The question describes the release of a mature ovum (egg) from the ovary into the oviduct (fallopian tube).

This specific event is known as ovulation.

• A: menstruation (Shedding of the uterine lining)
• B: fertilisation (Fusion of sperm and egg)
• C: implantation (Attachment of the embryo to the uterine wall)
• D: ovulation (Correct, the release of an egg from the ovary)

The final answer is $\boxed{\text{D}}$

13)

Puberty in girls involves physical changes such as breast development, growth spurt, onset of menstruation, and widening of the hips (pelvic girdle).

• A: widening of the pelvic girdle (Correct, this is a characteristic change in girls during puberty to prepare for childbirth)
• B: broadening of shoulders (More characteristic of puberty in boys)
• C: development of beard (Characteristic of puberty in boys)
• D: deepening of voice (Characteristic of puberty in boys)

The final answer is $\boxed{\text{A}}$