What upset their mother? Synthesis and Transformation

English quiz:

Synthesis and transformation takes up 10 marks in Paper 2. It’s not as tough as comprehension or vocabulary cloze– the nemesis of most students, so try to score in this category.

Many of my students were stumped by this question. It’s not tough but there are a few parts to the question which may lead to careless mistakes. Can you answer this?

Q: Sofia argued frequently with her brother. This upset their mother.
A: Sofia’s frequent_______________________________________

ANS: Sofia’s frequent arguments with her brother upset their mother. 

My students had a few problems with this question. 
1. They misspelled “arguments”- many wrote it as “arguements”
2. They thought the past tense of “upset” is “upsetted”
3. They forgot to include the plural form of “argument”

All these would incur loss of marks for the students.