What types of instruments are commonly used in surface observations?

The correct answer is grounded in the fundamental tools used to gather surface weather observations, which directly relate to measuring atmospheric conditions at ground level.

Thermometers measure temperature, providing crucial information about heat in the atmosphere which can influence weather patterns. Barometers measure atmospheric pressure, which is essential for assessing weather systems and predicting changes. Anemometers are used to measure wind speed and direction, vital components in understanding how air movement influences weather conditions. Hygrometers assess humidity, which significantly impacts precipitation and temperature dynamics. Together, these instruments provide comprehensive and critical data for analyzing and forecasting weather conditions at the Earth's surface.

Other choices, while they represent important meteorological tools, pertain to different aspects of weather observation or measurement that do not focus primarily on surface conditions. For instance, radar and satellites are primarily used for remote sensing and monitoring larger weather systems rather than direct surface measurements. Seismographs are utilized for detecting earthquakes and not related to meteorological surface observations. Altimeters are used in aviation to determine altitude and are not specifically designed for surface weather observations. Thus, the selection of thermometers, barometers, anemometers, and hygrometers encompasses the primary instruments for standard surface weather observations.