be slow in doing sth. = be slow to do sth.意思是”做某事慢吞吞的“。例如：The police were slow in coming . = The police were slow to come . 警察姗姗来迟。（外研社、建宏《英汉多功能词典》slow 词条）The idea was slow to gain general acceptance. 这种想法通常会慢慢得到赞同。