Question

when a star exhausts its core hydrogen, its core while the star as a whole contracts, expands, stays the same,

Explanation:

When a star exhausts its core hydrogen, nuclear fusion in the core stops. The core, no longer supported by the outward - pressure from fusion, contracts under its own gravity. Meanwhile, the outer layers of the star expand due to the energy released from the hydrogen - burning shell around the contracting core.

Answer:

The first blank: contracts
The second blank: expands