Answer:
I must always obey to my parents.
I mustn't steal anything from anyone.
In the sentence "They say we will not be able to afford to own houses in a few years." there's a <u>pronoun reference</u> error. It is unclear who the pronouns<em> they </em>or <em>we </em>are referring to.
Pronouns are used to replace nouns, and it is considered to be a pronoun reference error when the reader is unable to deduce from the text the noun being replaced by the pronoun.
Assuming nitrogen is an ideal gas, we use the relation PV=nRT tp predict what will happen to the system. From the equation, nR/P is constant. So, if the sample is cooled to 72K then volume would decrease. This decrease in volume would affect the density of the substance. It would increase its density. Therefore, the answer would be density.