Identify the option that would correctly fill in the blanks of the given paragraph.

Our science teacher (a) _________ to return the corrected test papers by noon on Monday. She, I (b) _________ sure, (c) _________ marking them by Monday morning. She (d) _________ us in the 'laboratory by 9 a.m. in the morning but (e) _________ our marks only when she (f) _________.

Option A is the correct answer:
(a) had promised: This refers to a completed action in the past (promised) relevant to the current situation.
(b) am: This indicates the speaker's current state of belief ("I am sure").
(c) would have finished: This is a hypothetical situation—if she had continued marking through the weekend, she would have finished by Monday morning.
(d) is meeting: This refers to a scheduled meeting happening in the present ("by 9 a.m. in the morning").
(e) would reveal: This refers to a future action that is dependent on another action ("only when she meets").
(f) meets: This refers to her habit or usual action ("when she meets").
Option B: had been promising: This suggests repeated promises in the past, which isn't necessary here.
Option C: will have finished: This suggests the marking will be finished in the future, which contradicts the context of Monday morning.
Option D: has promised: This is grammatically correct but less specific than "had promised," which emphasizes a completed promise.

Therefore, Option A is the correct answer.