Final answer:
The measuring cylinder with a least count of 1.0 ml will be preferred to determine the density more accurately.
Step-by-step explanation:
The measuring cylinder with a least count of 1.0 ml will be preferred to determine the density more accurately. The least count of a measuring instrument is the smallest quantity that can be measured with that instrument. In this case, the measuring cylinder with a least count of 1.0 ml allows for more precise measurements compared to the measuring cylinder with a least count of 2.5 ml.