What environmentally harmful isotope was produced during the 1954 'Bravo' thermonuclear detonation at Bikini Atoll?

What environmentally harmful isotope was produced during the 1954 'Bravo' thermonuclear detonation at Bikini Atoll?


W)Uranium 238
X) Nitrogen-15
Y) Cesium 137
Z) Carbon14


Answer: Y