Explanation:

- Anemometer: This instrument measures wind speed and direction. It has cups or blades that rotate in the wind, not related to measuring rainfall.

- Sling Psychrometers: Used to measure humidity. It has a wet and dry bulb thermometer to calculate relative humidity but doesn't measure rainfall.

- Standard Rain Gauge: Correct! It consists of a funnel-shaped collector attached to a measuring tube. It accurately measures rainfall per unit area.

- Hygrometer: Measures the moisture content in the atmosphere. Like the sling psychrometer, it deals with humidity, not precipitation.