Since most personal watercraft (pwc) do not have brakes, what must be done in order to avoid an obstacle?

With Personal Watercraft having no brakes, the best thing to do in avoiding obstacles is to take caution and slow down while operating the Personal Watercraft boat but when obstacles are ahead and you need to use methods, it is best to apply throttle and after that, steer quickly.

then that particular organisms become extinct.

"do a testcross with a homozygous recessive plant."