Answer:
Old Testament; One God; Holy Spirit.
Explanation:
The old Testament describes the old covenant the Lord made with the Israelites in the Bible and it consist of history of creation, how the Israelites are chosen, the journey of Isrealites, the time Isrealites were held captives in the Land of Egypt, the laws, the Judges and kinds of Israel and many more.
In the Old Testament more emphasis was based on one true God and little or nothing was actually said about the 'trinity' (although the words " spirit of God" was mentioned several times in the old Testament but there the emphasis on the doctrine of Blessed Trinity was not there).
In the New Testament, when Christ come for the atonement of Sin of Mankind, Jesus Christ made sure to show that the Trinity is one God that is God the Father, God the son and the Holy spirit are one.