A Christmas tree includes a main body, an bulkhead connector, a wet-mate connector, a cable, and a sensor. The main body has a first and a second main body end, and a further passage, and encloses a main passage. The further passage includes a first further passage end at a main body exterior and a second further passage end at the main passage, and extends from the first to the second further passage end. The bulkhead connector is secured to the main body exterior to close the first further passage end, and has a first and a second electrical connection. The wet-mate connector is mounted in the second further passage end to close the second further passage end. The cable transmits an electrical signal and connects the first electrical connection to the wet-mate connector. The sensor is arranged in the further passage and electrically connects to the second electrical connection.