Dear Professor Miller,
I am writing this letter to explain the reason for having low grade that I have been received for our last academic assignment.
All the project works had to be done by myself throughout the project. Even though my partner and I had divided tasks separately, I had to carry out all the phases of the project alone due to unavailability of my friend. Therefore, I was not able to manage my time properly.
The condition of my partner’s mother had changed the mind of my partner completely. His mother has been at the hospital for weeks, so he was not able to attend any project discussion meetings. Therefore, he had not proper idea about his role.
I would be grateful if you would allocate some extended period in order to re-submit our assignment. If I get some extra time, I will be able to plan the requirement-gathering stage in broad way instead of online survey. Then, more quality will be added into the project.
Yours sincerely,
Malinda Amunugama. 
Dear Professor Miller,
I am writing this letter to  
explain
 the reason for having low grade that I have  
been received
 for our last academic assignment.
All the  
project
 works had to  
be done
 by myself throughout the  
project
.  
Even though
 my partner and I had divided tasks  
separately
, I had to carry out all the phases of the  
project
 alone due to unavailability of my friend.  
Therefore
, I was not able to manage my time  
properly
.
The condition of my partner’s mother had  
changed
 the mind of my partner completely. His mother has been at the hospital for weeks,  
so
 he was not able to attend any  
project
 discussion meetings.  
Therefore
, he had not proper  
idea
 about his role.
I would be grateful if you would allocate  
some
 extended period in order to re-submit our assignment. If I  
get
  some
 extra time, I will be able to plan the requirement-gathering stage in broad way  
instead
 of online survey. Then, more quality will be  
added
 into the project.
Yours  
sincerely
,
Malinda  
Amunugama
.