Your question asks what specific service dimension is important for a salesperson to understand and what dimension is the sentence addressing.
The reason why "installation" would be the correct answer is because buyers want to make sure that they're getting whatever they're getting set up by the right people.
A sales person should know the installation service dimension in order to make sales, due to the fact that most buyers want someone that can come and install whatever they bought.
The sentence "Do we send a team to your site for start-up?" addresses installation because the salesperson is telling the buyer if they need to send their team to the buyer in order to install the start up that the buyer has.
