If a), there were no end to the backward regression, then not everything has a cause, because the regression itself ultimately had no cause. Therefore, either way there is someone/something that has no cause.
Kama a), kusingekuwa na mwisho wa kurudi nyuma kusikokuwa na ukomo, basi si kila kitu kingekuwa na chanzo kwa sababu kurudi nyuma kusikokuwa na mwisho kwenyewe hakuna chanzo. Kwa hiyo, kwa vyovyote vile kuna mtu/kitu ambacho hakina chanzo.