Question 24: Mark the letter A, B, C, or D on your answer sheet to indicate the unlined part that needs correction in each of the following questions: It is essential that cancer is diagnosed and treated as early as possible in order to assure a successful cure.
Knowledge of assumptions:
It + be + essential/ necessary/vital… that + S + V(infinitive)
=> The answer is B (is => be)
It is essential that cancer be diagnosed and treated as early as possible to ensure successful cure.