'Opklaren' and 'Verklaren' can have the same meaning: 'To make something clear'. 'To explain something.' But in the daily use of Dutch, 'Opklaren' means that the weather is improving, The sky is clearing up. One can say: 'Ik verklaar dat ik Nederlans ben.' ( i declare that I am Dutch) But one cannot say: 'Ik opklaar iets...' One can say: ' De zaak is opgeklaard'. ( The case is solved).