A packet of flour should weigh 250 g. Four students each weigh it three times on different scales…

A packet of flour should weigh $250\ \text{g}$. Four students each weigh it three times on different scales:

• A: $250\ \text{g}$, $251\ \text{g}$, $249\ \text{g}$
• B: $262\ \text{g}$, $263\ \text{g}$, $262\ \text{g}$
• C: $240\ \text{g}$, $260\ \text{g}$, $250\ \text{g}$
• D: $230\ \text{g}$, $275\ \text{g}$, $260\ \text{g}$

Say whether each set is accurate, precise, both or neither.