Which of the following is true when navigation with radar during restricted visibility （).

Which of the following is true when navigation with radar during restricted visibility ().① Radar may not indicate small vessels and icebergs;② Radar may mean that safe speed is even slower due to the indication of other vessels on the scope.

A.① only

B.② only

C.Both ① and ②

D.Neither ① nor ②

请帮忙给出正确答案和分析，谢谢！