What is the default version of nfs mount through busybox?

Issue

• Unable to mount nfs share through busybox while the same can be mounted through mount command.

# busybox mount -t nfs nfs-server:/test /mnt -vvv
mount: mount('nfs-server:/test','/mnt','nfs',0x00008000,''):-1: Protocol not supported
mount: mounting nfs-server:/test on /mnt failed: Protocol not supported

# mount -t nfs nfs-server:/test /mnt