The citizens welcomed all the African …

Analyze the question: This tests the plural form of compound nouns. The sentence says "all the African ......." so we need a plural form that refers to more than one leader.

Concept: In compound nouns made of a main noun plus a prepositional phrase (e.g., mother-in-law, commander-in-chief, head of state), the main noun takes the plural "s", not the end of the phrase.

• mother-in-law → mothers-in-law
• commander-in-chief → commanders-in-chief
• attorney general → attorneys general
• head of state → heads of state

Step-by-step solution:

1. "All the African ..." signals plural, because "all" means several leaders.
2. The main noun in the phrase is head (the person who leads). "of state" only describes it.
3. So we pluralise "head" and leave "state" singular, because it is one concept (the state as an institution): heads of state.
4. Check the options: • A. heads of states: wrongly pluralises "state" too. • B. heads of state: correct. • C. head of states: "head" is not pluralised, so it is wrong. • D. head of state: singular, so it does not agree with "all".

The sentence reads: The citizens welcomed all the African heads of state.

Answer: B

Tip: For compound nouns with "of" or "in", pluralise the first (main) word: heads of state, passers-by, brothers-in-law, men of war. Ask yourself, "Which word names the actual person or thing?" That is the one that takes the "s".