This sentence is in the passive voice, and it indicates that the subject (the work) will receive the action (be finished) performed by someone (me).
The original sentence, "I will finish the work tomorrow", is in the active voice, indicating that the subject (I) will perform the action (finish) on the work.
A. My father is talking to his friend on mobile phone when I fall from the bicycle
B. My father was talking to his friend on mobile phone when I fall from the bicycle.
C. My father was talking to his friend on mobile phone when I am falling from the bicycle.
D. My father was talking to his friend on mobile phone when I fell from the bicycle.
Explanation
The correct sentence is:
c. My father was talking to his friend on mobile phone when I fell from the bicycle.
This sentence correctly uses the past continuous tense ("was talking") for the ongoing action and the simple past tense ("fell") for the completed action.