Choose the part of the sentence that contains an error:
She does not know to swim.

Correct option is B

Option (b) contains an error.
Explanation: After know, when we talk about ability or method, the correct structure is know + how + to + V¹ (or use can + V¹). The phrase “know to swim” is unidiomatic in this sense. The sentence should be “She does not know how to swim.” Alternatively, “She cannot swim.”
Grammatical rule used:
· Use know how to + base verb to express knowledge of doing something (ability/method): know how to drive / cook / swim.
· Know + to + V¹ is grammatical in a different sense ( be aware that one should): He knows to be careful (i.e., he knows he should be careful), which is not the intended meaning here.
· Example:
· Correct: They know how to solve quadratic equations.
· Incorrect: They know to solve quadratic equations.
· Information booster: You may also use can/cannot + V¹ for general ability: She can swim / She cannot swim.