The difference between a job and work (countable/uncountable).
Here’s a simple way to distinguish between factor, reason and cause.
‘Whereby’ is a useful linking word but it only collocates with certain nouns – check which ones here.
‘Overwhelming’ is a useful adjective for emphasis. This blog reviews other uses of the prefixes ‘over’ and ‘under’.
‘Justify’ and ‘justification’ are powerful academic words and therefore excellent to use in formal essays.
Using expression to question how much can be guaranteed (e.g. websites that guarantee Band 7) shows critical thinking – see how to use it here.
‘In case of’ might not have the meaning you think it has – see the issues it causes here.
‘Consideration needs to be given to’ is such a nice formal expression that you can apply to many different topics.
There are many useful collocations for ‘benefit’ that will strengthen your arguments. Practise them here.