How to check uniform continuity on r

2 Let f: R R and g : la, b] > R 1. be defined as flx) =x Vx e R and glx) = * Vxe la, b]. Then : (A) f and g both are uniformly continuous (B) fis uniformly continuous and g is continuous (C) f is continuous and g is uniformly continuous (D) fand g both are continuous but not uniformly continuouus