In Terms of Sequencing, Mixed Method Designs Can Either Be

In terms of sequencing, mixed method designs can either be concurrent or sequential. What is a concurrent design?

A) Both strands occurring in one simultaneous phase.
B) Both strands occurring prior to informing the third and fourth strand.
C) One strand occurring prior to and informing the second strand.
D) Two strands occurring prior to and informing the third and fourth strand