The correct preposition to use in this sentence is "to". The phrase "find it hard to" is commonly used to express difficulty in doing something.
The sentence becomes:
He found it hard to contain his anger.
The correct preposition is "to".
Each question has a sentence that has an underlined part. Choose the option which rephrases the underlined part in the most appropriate manner in terms of grammar and usage.
In an attempt to boost their profits, many edible oil-producing companies have been engaging themselves in propaganda against commonly used oils and promoting exotic and expensive varieties of oils \(\underline{as\ more\ healthier\ options.} \)