The student measured the volume of water as 80.0 ml. she discovered that the actual volume was 80.1 ml. is her measurement accurate

Yes, her measurement is accurate.

Accuracy of a measurement is the closeness of a measured value to the actual or standard value. From the question, the first volume she measured; 80.0 ml is closer to the actual volume of water; 80.1ml. In this case, her measurement is accurate.

 In general mutations often occur during nuclear division because each chromosome has to replicate before division (mitosis). During replication your 3 billion nucleotides make copies of themselves leaving one copy in the original cell and another in the sister cell after division. This as you can imagine makes mutations most likely to occur here.