When raw spaghetti cooks to al dente, what happens to its starch?

Answer: It absorbs water and softens

It absorbs water and softens ✓ — Right. At al dente, heat and water have hydrated the starch enough to remove the chalky raw taste, while the dense center still gives resistance. The starch stays inside the noodle instead of flooding into the cooking water. That controlled hydration is the boundary from raw to al dente.

It dissolves into the cooking water — No. If starch fully dissolves into the water, the noodle has gone past al dente toward soft and sticky. The starch that leaks out can thicken pasta water, but losing too much weakens the noodle's own structure. Al dente sits before that heavy release.

It stays dry and raw — No. A firm center is not a dry raw core. In al dente pasta, enough water has moved in to cook away the chalky rawness, but not so much that starch floods out. The bite comes from controlled hydration, not dryness.