Which sentence uses commas correctly?

a.
at each stop, in the treasure hunt we found an envelope with a clue.

b.
at each stop, in the treasure hunt, we found an envelope with a clue.

c.
at each stop in the treasure hunt, we found an envelope with a clue.

d.
at each stop in the treasure hunt we found an envelope with a clue.

Which sentence uses the verbs correctly?

These two elements threaten ecosystem biodiversity.

Of all the attributes essential to a respected man or woman or to a respected nation, the predominant characteristic is self-discipline. laws cannot be made compelling people to suppress their desire for power or position. no method of legislating such wisdom exists. as free people, we must face a choice between two types of discipline. one is the self-discipline that is still open to us—the kind that free people and free nations exercise when they select the executives, lawmakers, and judges who will govern them and assure their protection and well-being. the second is a cold-blooded, ill-intentioned, form of discipline that may be thrust upon us by strangers—the discipline of force, terrorism, suspicion, and intimidation—the discipline used in totalitarian regimes.does every sentence following the first in some way support the theme?