From the choices above,the next steps are these following answers (arranged from left to right):
In the white boxes
Rhizobia release a chemical, causing an infection thread to form ► Infection thread grows into the cortex of the root ► Infection thread releases rhizobia inside cortex cells. ► Nodule forms from rapidly dividing cortex cells
In the blue boxes
respond to rhizobia signals and produce infection thread ► extend infection thread into cortex ► allow infection thread to rupture ► cause cortex cells to divide rapidly upon contact with rhizobia