What is a cause of humans' negative biological reaction to loneliness?
A、The requirement of family groups.
B、The dependence on social support.
C、The destruction of the environment.
D、The improvement of living conditions.
I.Phonetics(5 points)Directions:In each of the following groups of words, there are four underlined letters or letter combinations marked A, B, C and D. Compare the underlined parts and identify the one that is different from the others in pronunciation. Mark your answer by blackening the corresponding letter on the Answer Sheet.1.( )