3차원배열까지 선언해서러나 이딴오류뜸 ... 머져이거?

tajap.c: In function ‘main’:
tajap.c:78:2: warning: passing argument 1 of ‘strlen’ from incompatible pointer type [enabled by default]
  typing_per_sec = strlen(longsent[x]) / typing_sec;
  ^
In file included from /usr/include/stdio.h:29:0,
                 from tajap.c:1:
/usr/include/string.h:33:9: note: expected ‘const char *’ but argument is of type ‘char (*)[100]’
 size_t  _EXFUN(strlen,(const char *));