. Which of the following would indicate a new substance has been formed?

There are signs that a chemical reaction occurs. Bubbles form, a gas is given off, and the beaker gets very hot. The most important sign that a chemical reaction occurs is the formation of new substances. The new substances are carbon, a brittle black solid, and water vapor, a colorless gas.

Explanation:

b) the planets year length would be longer

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the correct answer is modern american cars are not available due to trade restrictions.

trade between cuba and the united states have serious restrictions. the u.s. imposed an economic embargo on cuba, that among other things means that modern american cars are not available due to trade restrictions.

in response to some governmental actions of the authorities from cuba, president john f. kennedy proclaimed an embargo on trade between both countries in february 1962. the trade embargo remains active until this day and was implemented directly by the departments of commerce and the department of treasury.

in president trump’s administration, there is a national security presidential memorandum that "strengthens the policy of the u. s.", affecting trade with cuba.