What is a regular language?

A$.$ Any language that is easy to learn

B$.$ A language that can be expressed by a regular expression

C$.$ A language that requires advanced programming skills

D$.$ A language used in regular communication

Which of the following is a characteristic of a regular grammar?

A$.$ It can generate context$-$free languages

B$.$ It can generate non$-$regular languages

C$.$ It has productions of the form $AaB$

D$.$ It involves complex mathematical operations