Error spotting in tense and modal usage: She told her teacher that she could not be able to attend the class the previous day because of heavy rains. Identify which part of the sentence is wrong or state that there is no error.

Introduction / Context:
This question examines correct usage of modal verbs and expressions of ability in reported speech. The sentence describes a girl explaining to her teacher why she missed class. The phrase could not be able is faulty because it unnecessarily combines a modal verb with a separate expression of ability. Competitive exams frequently test this area to ensure that learners avoid redundant or ungrammatical combinations.

Given Data / Assumptions:
- Sentence: She told her teacher that she could not be able to attend the class the previous day because of heavy rains.
- The reporting clause is She told her teacher that.
- The reported clause explains her inability to attend class due to heavy rain on the previous day.
We assume a standard past time frame and formal written English.

Concept / Approach:
In English, we express inability in the past using either could not plus base verb or was not able to plus base verb. We do not combine these forms as could not be able to. The correct options are could not attend the class or was not able to attend the class. Therefore, the verb phrase could not be able to attend is redundant and ungrammatical. The remaining parts of the sentence, including the time expression the previous day, are acceptable.

Step-by-Step Solution:
Step 1: Identify the reporting verb: told. This is correct for indirect speech in the past tense. Step 2: Examine the embedded clause beginning with that she could not be able to attend the class. Step 3: Recall the rule that could not already expresses inability, so we pair it with a base verb such as attend. Step 4: The correct alternatives are she could not attend the class or she was not able to attend the class. Step 5: The phrase the previous day correctly indicates a day before the time of reporting in indirect speech. Step 6: Because of heavy rains is also a correct causal expression. Hence the only error lies in the verb phrase could not be able to attend the class.

Verification / Alternative check:
We can construct two corrected versions for verification: Correct version 1: She told her teacher that she could not attend the class the previous day because of heavy rains. Correct version 2: She told her teacher that she was not able to attend the class the previous day because of heavy rains. Both versions are grammatical and convey exactly the same meaning as intended. In both cases the redundancy is removed, confirming that the original phrase could not be able was wrong.

Why Other Options Are Wrong:
- Error in the time expression the previous day only: The time reference is correct for reported speech referring to yesterday, so this is not an error.

- No error in any part of the sentence: This ignores the clearly redundant and ungrammatical form could not be able, so it is incorrect.
- Error in both the verb phrase and the time expression: As the time phrase is correct, claiming two errors is wrong.
- Error in the reporting verb told only: Told is the normal past tense form used for reporting, so there is no problem with this verb.

Common Pitfalls:
A common learner mistake is to assume that combining different expressions of inability makes a statement stronger, so they produce forms like could not be able or did not could. However, English prefers clear, single structures. When using a modal like can or could, follow it directly with the main verb. When using be able to, use it with appropriate tense of be and do not add another modal in front. Regular practice with pairs such as can attend and am able to attend, or could attend and was able to attend, can help avoid this redundancy.

Final Answer:
Correct option: Error in the verb phrase could not be able to attend the class.