New home build - cracks in basement concrete floor
Those "straight lines" are control joints (as opposed to expansion joints). The contractor knows that concrete slabs invariably crack, and they install those to make the cracks less conspicuous.

That said, you do seem to have more cracks than I'd have expected, and they appear more open than is typical. The one is oddly close to the exterior wall. I'd ask your builder about backfill and compaction practices.