we will have to set up a … panel to investigate this matter

Analyze the question: The blank comes before the noun "panel" and needs a compound adjective that describes the panel. The question tests how compound adjectives are formed.

Concept: When a number and a noun combine to modify another noun, they are joined with a hyphen. The noun inside the compound stays singular, even when the number is more than one.

Examples:

• a five-year plan (not "five-years plan")
• a two-bedroom flat
• a three-man committee
• a ten-naira note

Step by step:

1. The phrase must describe "panel", so it works as an adjective.
2. Adjectives in English do not take plural forms, so "men" is wrong. This rules out A and B.
3. C, "seven man", has no hyphen, so the compound is not properly formed. It would read as two separate words.
4. D, "seven-man", is a hyphenated compound adjective with a singular noun. It is correct.

Correct sentence: We will have to set up a seven-man panel to investigate this matter.

Answer: D.

Exam tip: Remember the rule "number + hyphen + singular noun" before another noun. If you can write "a ___-year plan" correctly, you can handle "seven-man panel". Never put an "s" on the noun inside the compound.