the command `bitcoin-cli dumpwallet walletfilename` shows
# extended private masterkey: tprv8ZgxMBicQKsPdXHSRpLtX329KK4Phqx3T2dMkiKK427K7yCqUbfK1NtQYdyFSsCsdbv5Emce61p ZY7TFXc3jvxMtPFzChbwxH5g6XCm9e6m
cUGWMsLyd7MBffw6poDHEiDoWXv2aqrHi1RcLSQ7C4yhAQMBdcYs 1970-01-01T00:00:01Z label= # addr=mgYCPhE63MQsB8hd66ZZYEGDZTETf9WrqF
.....
cUPRHPYeTefm566zr4iA5v7uqvwyQg9VqXAQfGqkRC8bGvf3pxSR 2018-04-27T03:58:55Z reserve=1 # addr=mfXfTUL9XRF7jFtruu6z3nxH7oiX7APuQT hdkeypath=m/0'/0'/740'
which one is the xprv key ?