According to the findings from the Știll - Face Paradigm research, how do infants react during the still - face episodes?

A. Infants show increased interest and engagement with their mothers.
B. Infants quickly become distressed when mothers do not express emotion or react.
C. Infants remain unaffected by their mothers' neutral expressions.
D. Infants exhibit a decline in emotional distress and look at their mothers longer.