Take the following as truth: A new alliance with England was sealed in the 1386 Treaty of Windsor; a year later Joao of Avis married Philippa of Lancaster, the daughter of John of Gaunt.
Then the following statement: "The marriage of Joao of Avis and Philippa of Lancaster would not have been possible before the alliance with England that had been formed the year before." is true, false, or inconclusive?