1. (2007 Hebei Province High School Mathematics Competition) Among the four functions (1) $f(x)=x^{3}$, (2) $f(x)=1-x^{2}$, (3) $f(x)=|\tan x|\left(-\frac{\pi}{2}<x<\frac{\pi}{2}\right)$, (4) $f(x)=2 x+1$, the number of functions that satisfy the condition $f\left(\frac{x}{3}+\frac{2 y}{3}\right) \geqslant \frac{1}{3} f(x)+$ $\frac{2}{3} f(y)$ is
A. 1
B. 2
C. 3
D. 4
1. $\mathrm{B}$
(2) (4) meet the conditions.