A Source of Frequency F Sends Waves of Wavelength $\lambda$ Traveling with Speed V in Some Medium

Multiple Choice

A source of frequency f sends waves of wavelength $\lambda$ traveling with speed v in some medium.If the frequency is changed from f to 2f, then the new wavelength and new speed are (respectively) :

A) "2 $\lambda$ , v"
B) " $\lambda$ /2, v"
C) " $\lambda$ , 2v"
D) " $\lambda$ , v/2"
E) " $\lambda$ /2, 2v"