4.给出以下4个命题①若lim_(x to 0)f(x)=a，且lim_(x to 0)varphi(x)=0，则lim_(x to 0)f[varphi(x)]=a.②若f(x)在x=0处连续，且lim_(x to 0)varphi(x)=0，则lim_(x to 0)f[varphi(x)]=f(0).③若lim_(x to 0)f(x)=a，且lim_(x to 0)(varphi(x))/(x)=1，则lim_(x to 0)f[varphi(x)]=a.④若lim_(x to 0)f(x)=a，且极限lim_(x to 0)(varphi(x))/(x)存在，则lim_(x to 0)f[varphi(x)]=a.其中真命题个数为（）A. 0.B. 1.C. 2.D. 3.

4.给出以下4个命题 ①若$\lim_{x \to 0}f(x)=a$，且$\lim_{x \to 0}\varphi(x)=0$，则$\lim_{x \to 0}f[\varphi(x)]=a$. ②若f(x)在x=0处连续，且$\lim_{x \to 0}\varphi(x)=0$，则$\lim_{x \to 0}f[\varphi(x)]=f(0)$. ③若$\lim_{x \to 0}f(x)=a$，且$\lim_{x \to 0}\frac{\varphi(x)}{x}=1$，则$\lim_{x \to 0}f[\varphi(x)]=a$. ④若$\lim_{x \to 0}f(x)=a$，且极限$\lim_{x \to 0}\frac{\varphi(x)}{x}$存在，则$\lim_{x \to 0}f[\varphi(x)]=a$. 其中真命题个数为（）

A. 0.

B. 1.

C. 2.

D. 3.