Question

He tried to solve the sum but _________ not.

1. Can 2.Could
3. May 4. Might​

Answer 1

He tried to solve the sum but could not.

Explanation:

• Could is a modal verb (special verbs that behave irregularly) used to express past ability or possibility.  for example, I could speak German when I was in college.
• Could is used to make requests and suggestions, examples, Could I use the restroom please? You could spend your summer vacation in Canberra.
• Could is also often used in conditional sentences ( sentences conveying   hypothetical situations/factual implications and their outcomes/consequences) as the conditional form of can, for example,  If I had more time, I could travel around the world.
• When could is used as the past tense of can, it denotes an ability which a person usually had in the past or to something which was possible in the past

Answer 2

Answer:

2 could is the right answer

Explanation:

could it's so easy