  Inspired by the recent report of the exotic states $X_{0}(2900)$ and
$X_{1}(2900)$ with four different quark flavors in the $D^{-}K^{+}$ invariant
mass distributions of the decay process $B^{+}\rightarrow D^{+}D^{-}K^{+}$ by
the LHCb collaboration, we systematically investigate the tetraquarks composed
of $ud\bar{s}\bar{c}$ with meson-meson and diquark-antidiquark structures in
the quark delocalization color screening model. We find that the $X_{0}(2900)$
can be interpreted as the molecular state $\bar{D^{*}}K^{*}$ with
$IJ^{P}=00^{+}$. Moreover, two bound states are obtained by the channel
coupling calculation, with energies $2341.2$ MeV for $IJ^{P}=00^{+}$ and
$2489.7$ MeV for $IJ^{P}=01^{+}$, respectively. We also extend our study to the
$uc\bar{d}\bar{s}$ systems and find that there is no any bound state, so the
$D_{s0}(2317)$ cannot be identified as the $DK$ molecular state in present
calculation. Besides, several resonance states with the diquark-antidiquark
configuration are possible in both $ud\bar{s}\bar{c}$ and $uc\bar{d}\bar{s}$
systems. All these open charm bound states and resonances are worth searching
in the future experiments.
