[单选题]
A string of mass m and length L is under tension T. The speed ooxtqx9iz6 -e :f a wa i)atu(: t.nipve in the string is v. What will be the speed of a wave in the strit:ai)(.iut p nng if the length is increased to 2L, with no change in mass?
A. $0.5 \; v$
B. $0.71 \; v$
C. $1.4 \; v$
D. $2 \; v$