The doctor declared that the sick child needed a blood …

Analyze the question: The sentence is about a sick child who needs a blood __. We need the word that describes putting blood from one person into another's body.

Explain the concept: This is a vocabulary question on words that start with "trans-", which means "across" or "through". Each word has a different meaning:

• Transformation: a complete change in form or appearance (e.g., a caterpillar's transformation into a butterfly).
• Transfer: moving something or someone from one place to another (e.g., a school transfer, a bank transfer). It is not the medical term for blood.
• Transmission: passing something on, such as a disease, a signal, or a car's gears.
• Transfusion: the medical process of introducing blood (or blood products) into a person's bloodstream.

Step-by-step solution:

1. The phrase is "a blood __", so the missing word must be a medical term that goes with blood.
2. "Blood transformation" has no medical meaning.
3. "Blood transfer" is not the standard term.
4. "Blood transmission" is about spreading something, like infection, and is not what a doctor prescribes for a sick child.
5. "Blood transfusion" is the correct collocation, meaning giving blood to a patient who has lost blood or is severely anaemic (as in cases of sickle cell crisis or malaria complications, common in Nigeria).

Correct answer: D. transfusion

Tip: Remember that transfusion contains "fuse/fuse in", which suggests pouring or flowing in, like blood flowing into a patient. Also memorize common collocations such as blood transfusion, blood pressure, blood donor, and blood bank. WASSCE and JAMB often test these.