  The $\textit p_{T}$-differential cross section of D mesons in the rapidity
range $|y|< 0.5$ was measured in pp collisions at $\sqrt{s}$ = 2.76, 7 and 8
TeV. D mesons were reconstructed in their hadronic decay channels by means of
the invariant mass analysis. The D-meson production cross sections is compared
among different energies and to pQCD calculations. Also the prompt D meson are
studied as a function of the multiplicity of charged articles produced in
inelastic pp collisions at a centre-of-mass energy of $\sqrt{s}$ = 7 TeV. The
measurements are compared with model calculations.
