How does uncertainty relate to measurements and calculations made during an investigation?

There is uncertainty in each measurement, as indicated by significant figures.

There is uncertainty in each count of items used in a procedure.

There is no uncertainty in an answer calculated using significant figures.

There is no uncertainty if the best equipment is used correctly.

There is always uncertainty. The last two choices are not correct.

For the first two you can argue.

On the first premise, Uncertainty is symbolized by significant figures, this allows you to get closer to the real value but never reach the real value. As there will always be discrepancy even to the smallest increment for when measurements are involved due to many factors (calibration of equipment, reference values, location, human factor, etc ...)

On the second premise, for each items used in the investigation, it will always introduce margin of error. This is again attributed by many factors (human factor, calibration and many more.)

Uncertainty can be reduced but never eliminated when we talk of measurements,