Answer:
A. struggle to get a foot in the door
Explanation:
The example of pen was used to define the fact that most salespeople start off by asking or telling the usual instead of analysing the situation and determining the right questions to be asked from the customer which ultimately leads to most of sales individuals to struggle.
Like in this case where a salesperson is given a pen, he would start by saying that he has a pen to sell with multiple colours, they are affordable and lightweight. These questions are too generic and may not interest the customer. Instead to sale better one must ask intelligent questions that will be relevant for the customer in order to pitch them the right kind of product.
