the obligate parasite requires strigolactones for seed germination and not karrikins. The plant secrete strigolactone from its root into the soil as mentioned. In the soil, strigolactone promotes the seed germination of the parasitic weed.
The strigolactones can be beneficial for the germination and growth of the weed plant.
B. Runs his dishwasher only when it’s full.
All the rest seem like ways to waste water so I think B makes the most sense
