Spanish verbs ending in -car replace the -c- with a -qu- in El Presente de Subjuntivo. This is to preserve the sound from the infinitive.
Here is the conjugation of buscar (to look for) affected by this spelling change:
|él / ella / Ud.||busque|
|nosotros / nosotras||busquemos|
|ellos / ellas / Uds.||busquen|
Read and listen to these examples:
There are other useful verbs that have the same c > qu spelling change. For example: aparcar (to park), modificar (to modify), explicar (to explain) or equivocarse (to get something wrong).
Look at and listen to these examples: