Sign language is said to be very vivid and exact and can be used internationally except for （）

A．to make some sound experiments in the oceans
B．to collect samples of sea plants animals
C．to estimate the length of cable that was to be made
D．to measure the depths of two oceans

A．An urgent need for contact with adult.
B．A child’s efforts to be independent.
C．A child’s unsureness.
D．A child’s making statements about his own cleverness.