数列{a_n}的前n项和为S_n，若a₁="1," a_n+1 =3S_n(n ≥1),则a₆=（   ）

A．3 ×4⁴

B．3 ×4⁴+1

C．4⁴

D．4⁴+1

The dense black cumulonimbus clouds surrounding the eye of a hurricane are called（）.

A.Spiral rainbands

B.Cloud walls

C.Funnel clouds

D.Cyclonic spirals