Why does Amazon need to worry about competitors in online shopping?

Question $17$ options:

A$)$

The Internet increases switching costs.

B$)$

Internet technologies are universal, and therefore usable by all companies.

C$)$

E$-$commerce is affected by the law of diminishing returns.

D$)$

Internet shopping can take place $24/7$ in any location.

E$)$

The Internet enables the creation and sale of smart products.