The solution contains answers to multiple-choice questions on human digestion, respiration, malaria, and safe sex. What were the original questions?

Here are the answers to the multiple-choice questions:

11. The diagram shows a section of a human alimentary canal.

• F represents the upper part of the alimentary canal (mouth/esophagus), where digestion of carbohydrates begins.
• G represents the stomach, where digestion of proteins begins.
• H represents the small intestine, where the digestion of lipids primarily occurs and is completed.

Therefore, the correct option is A.
$\boxed{\text{A}}$

12. The following equation represents respiration in living organisms:
Glucose $\rightarrow$ X + carbon dioxide + energy (210KJ)
The production of carbon dioxide and a relatively small amount of energy (210KJ) from glucose indicates anaerobic respiration in the form of alcoholic fermentation. In this process, glucose is broken down into ethanol, carbon dioxide, and energy.

Therefore, substance X is Ethanol.
$\boxed{\text{A}}$

13. Which of the following is the causative agent for malaria?
Malaria is caused by parasitic protozoa of the genus Plasmodium, which are transmitted to humans through the bite of infected female Anopheles mosquitoes.

Therefore, the correct option is C.
$\boxed{\text{C}}$

14. Which of the following is a safe sexual practice?

• Consistent and correct use of condoms is a safe sexual practice as it significantly reduces the risk of transmitting sexually transmitted infections (STIs) and prevents unwanted pregnancies.
• Having multiple sexual partners, unprotected sexual intercourse, and sharing contaminated body fluids all increase the risk of STIs and other health issues.

Therefore, the correct option is A.
$\boxed{\text{A}}$

15. Which of the following correctly shows the functions of the solid parts of blood?

• Erythrocytes (red blood cells) are responsible for the transport of oxygen.
• Leucocytes (white blood cells) are involved in the defence against pathogens as part of the immune system.
• Thrombocytes (platelets) are essential for blood clotting.

Therefore, the correct option is D.
$\boxed{\text{D}}$