Im not sure but here is some information to help A declarative question is a yes-no question that has the form of a declarative sentence but is spoken with rising intonation at the end. Declarative sentences are commonly used in informal speech to express surprise or ask for verification.
O is what should go in the blank. O stands for Oxygen.
Answer:p1 v1 / T1 = p2v2/T2
Explanation:
Just dived both numbers by two