The options show various uses of strncpy. Choose which use of strncpy is most secure while not wasting storage space at dst? Src is an untrusted input obtained from an external source.
Strncpy(dst,src,len(dst))
Strncpy(dst,src,len(src)+1)
Strncpy(dst,src,len(dst)+1)
Strncpy(dst,src,len(dst)-1)