21. among the different kinds of flood basalt, the sio, content is highest in: acontinental tholeiites b. oceanic tholeiites c. alkaline olivine basalts d) spil

I think it should be A. Continental tholeiites consist majorly of SiO2, K2O and are more evolved as compared to the one that belong to oceanic tholeiites. Alkali Olivine Basalt, ...