Choose the option that rewrites the given sentence using ‘so ... that’ without changing its meaning:
The sum on the blackboard was too difficult for the students to solve.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → The sum on the blackboard was so difficult that the students could not solve it.
Changing “too ... to” into “so ... that ... not”:
- “Too difficult for the students to solve” means it was so difficult that they could not solve it.
- In the “that” clause, “not” comes in, the past tense stays (“could”), and the object comes back as “it”.
Why the Other Options are Incorrect?
Option 2: The sum on the blackboard was so difficult that the students could not solve. — Incorrect. The option ends with “could not solve”. In a “that” clause, “solve” needs its object, “it”.
Option 3: The sum on the blackboard was so difficult that the students could solve it. — Incorrect. This changes the meaning. It says the students could solve the sum.
Option 4: The sum on the blackboard was too difficult that the students could not solve it. — Incorrect. The option says “too difficult that”. “That” goes with “so”, not with “too”.