Which example is of researcher bias in interpreting data?

A scientist wishes to determine the area of an ice sheet. To do so, he relies on spectrographic images sent by satellite.


A health official investigates the spread of HIV in her city. She takes a census of the HIV status of every adult resident.


A geologist wants to determine whether the water level of an aquifer is declining. To find the answer, he digs a well.


A researcher seeks to prove that babies smile at two months old. She counts some confused expressions as smiles.