[单选题]
A string of mass m and length L is under tension T. sw e6) c+axaf (1l0qbrThe speed os)p. kf,fz ea lqk9g:/f a wave in the string is v. What will be the speed of a wave in the string if the :.9ezq, /kpk)aslgf flength is increased to 2L, with no change in mass?
A. $0.5 \; v$
B. $0.71 \; v$
C. $1.4 \; v$
D. $2 \; v$