Re-write the following sentences according to the instructions given after each. Make other changes that may be necessary, but do not change the meaning of each sentence.
If Mary catches the first bus, she will be on time for school. (Begin: Unless ..................)
Topic: Transformation — 'unless'
Answer
Unless Mary catches the first bus, she will not be on time for school.
UNLESS means IF NOT, so converting from a positive "if" requires the MAIN CLAUSE to become negative: Original: IF Mary catches the bus, she WILL BE on time. Unless: UNLESS Mary catches the bus, she WILL NOT BE on time.
Note where the negative goes. The condition clause stays POSITIVE — "unless Mary catches" — and the negative attaches to the RESULT. Writing "Unless Mary does not catch the bus" is a double negative and reverses the meaning, and it is the commonest error in this transformation.
THE TEST: read your answer and ask whether it gives the same information as the original. Both versions must mean that catching the first bus is what gets her there on time.
This transformation appears in SEVEN of the eleven papers in this subject. It is the single most frequently examined item in Question 5(d) / 4(d), and is worth drilling on its own.