2. (2004 National College Entrance Examination - Jiangsu Paper) The smallest positive period of $y=2 \cos ^{2} x+1(x \in \mathbf{R})$ is
A. $\frac{\pi}{2}$
B. $\pi$
C. $2 \pi$
D. $4 \pi$
2. B $y=2 \cos ^{2} x+1=\cos 2 x+2$, so $T=\pi$