单项选择题Whatisthedifferencebetween1+1and1:1protectionswitching?()
A. 1+1 is based on APS, while 1:1 is based on IPS.
B. 1:1 is used in SNCP switching, while 1+1 is used in MS-SPRing switching.
C. 1+1 sends signals on Working and Protect paths, while 1:1 sends signals only on Working path.
D. 1+1 sends signals on Working path ONLY, while 1:1 sends signals on both Working and Protect paths.