4. Given the equation $|x|=a x+1$ has one negative root and no positive root, then the range of values for $a$ is
(A) $a>-1$;
(B) $a=1$;
(C) $a \geqslant 1$;
(D) None of the above.
4. (C)

Translate the text above into English, please retain the original text's line breaks and format, and output the translation result directly.