Institution: Bangladesh Public Service Commission (BPSC) Exam: 10th BCS Preliminary Exam 1990
Topic: Correction (Sentence Correction), Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The correct option is 'A) Maria, my student. is on leave today' due to several factors regarding punctuation and sentence structure.

Firstly, the phrase "Maria, my student" uses a comma appropriately to set off the appositive "my student," which provides additional information about "Maria." This shows a clear relationship between the noun and its descriptor, indicating that "my student" is referring to "Maria."

However, the sentence includes a mistake: there should be a comma instead of a period before "is on leave today." The correct punctuation would be "Maria, my student, is on leave today." The use of a period after "student" separates the thought improperly.

Let's analyze the other options:
- **B)** lacks a comma after "Maria," leading to confusion and misreading the subject.
- **C)** introduces a misspelling with "toda" instead of "today."
- **D)** misplaces the commas, making it difficult to identify the subject of the sentence.

Overall, the intention of Option A is coherent, but it contains an error with the period. Properly correcting the punctuation would create a clear, grammatically accurate sentence.