Which is the best way to carry out?

[answerhappygod]

A service desk team is consistently receiving poor customer feedback that highlights a slow and ineffective service. Which is the best way to carry out an assessment that focuses on an appropriate scope and discovers what is contributing to the poor service?
OPTIONS

The assessment should focus on incidents handled by the service desk team
The assessment should focus on the overall service desk team
The assessment should focus on the service management practices of the whole IT department
The assessment should focus on the wider enterprise