Ascientist needs to know the temperature of the water every 5 m along 3 km of the river. what tool would the scientist use?

Thermometer is the best tool.

Explanation:

The temperature measurements can be made with a Celsius mercury thermometer, it must have a scale marked at least every 0.1 ° C recorded in the capillary glass and a minimum thermal capacity to allow a rapid equilibrium.

The best is an electronic digital thermometers, because it  provides reliable measurement of temperature in a wide range of temperatures

advantage of using stem cells in medical research:

1.       it provides medical benefits in the fields of therapeutic cloning and regenerative medicine.

2. it provides great potential for discovering treatments and cures to a variety of diseases including parkinson disease, spinal cord injuries, diabetes, alzheimer’s disease and many more.

3. limbs and organ could be grown in lab from stem cells and then used in transplant or treat illness.