The tone of this passage can be best expressed as ______.

A．the relationships between the salesperson and the customer and the packaging of the product play a very important role in selling process
B．the first thing people should care about is quality
C．American company is wiser than German company
D．you can take any measure in order to promote sales

A．the number of items to be put in a package
B．the taboo of a certain culture
C．the size and the color
D．all of the above