Which of the following is the most true regarding networking and the OSI Network Model?

a$.$ The OSI Network Model is only used with cell phone networks running $4$G or later.

b$.$ Any company making network hardware or writing network code is legally obligated to

use the OSI Model.

c$.$ Very few pieces of hardware or software follow the OSI Network Model because

monolithic network stacks are no longer used.

d$.$ Almost any company making network hardware or writing network code will use the OSI

Model instead of using a monolithic network model, because it makes it simper to

integrate their product with other network hardware and software.