A or B

Insure vs. Ensure

Insure is to provide financial protection against potential loss. Ensure is to make certain or guarantee that something will happen or be the case.
A or B

Tomatoes or Tomatos

Tomatoes is the plural form of "tomato", which is a fruit/vegetable used in various dishes. Tomatos is the incorrect variant of the word.
A or B

Independent vs. Dependent Variable

Independent variable is the variable that researchers change in an experiment to observe its effect on another variable. Dependent variable is affected as a result of changes in the independent variable.
A or B

Skillset or Skill set

Both words refer to a person's skills and abilities; the difference in use pertains to many factors.
A or B

Among vs. Amongst

Among and amongst both refer to being in the midst of a group . However, "among" is more common in American English, while "amongst" is more commonly used in British English.
A or B

Per Say or Per Se

Per se is used to emphasize that something is considered in and of itself, while per say is the incorrect usage of this term.
A or B

Sometime vs. Some time

Sometime is an adverb that refers to an unspecified point in time in the future or past. Some time, as a phrase, typically refers to a period of time that is not precisely defined.
A or B

Due to or Do to

Due to is a prepositional phrase that is used to indicate the cause or reason for something. Do to is an incorrect English phrase.
A or B

Everytime or Every time

Everytime or Every time both refer to each occurrence or instance of an event or action, but "every time" is the standard form in written and formal communication.