Questions

The size of gear is usually specified by pitch circle diameter.

"The moon smiled at me" is the example of personification in the given options.

Personification is a technique in which we give objects human traits like emotions, gestures, speech,... by using metaphor. 

Here moon is an object which cannot smile but using metaphor sense, we gave that sense to it.

llanos is a tropical grassland while the remaining three are temperature grasslands

Can’t delete a row from primary table if there are related rows in secondary table.

The inherited traits of an organism are controlled by DNA molecules.

The traits an organism displays are ultimately determined by the genes it inherited from its parents, in other words by its genotype. Animals have two copies of all their chromosomes, one from each parent.