Assertion (A): In TE10 mode the cutoff frequency of rectangular waveguide is where a is the broad dimension and c is velocity of light. Reason (R): TE10 mode is the dominant mode in rectangular waveguide.

• Both A and R are correct and R is correct explanation of A
• Both A and R are correct but R is not correct explanation of A
• A is correct but R is wrong
• A is wrong but R is correct