Select the correct option from the given alternatives: A trigonometric equation is called principal solution if A) `0 le alpha lt 2pi` B) `-2pi le alpha lt 2pi` C) `-frac{pi}{2} le alpha lt frac{pi}{2}` D) `0 lt x lt 2pi`

Options

A. `0 le alpha lt 2pi`
B. `-2pi le alpha lt 2pi`
C. `-frac{pi}{2} le alpha lt frac{pi}{2}`
D. `0 lt x lt 2pi`