The correct answer to this open question is the following.
Although the question does not include options, we can say the following.
Many theorists believe that important aspects of the acquisition of grammar are biologically predetermined. To determine what knowledge is innate, it has been especially helpful to design cross-linguistic studies of what is hard and what is easy for children to acquire.
With studies like the above-mentioned, theorists consider that teachers could have a better idea of how to help children learn. Not all children are equal. They have a different set of skills and abilities that teachers have to consider in the classroom. In many cases, teaching grammar is not an easy thing to do for teachers because not all children have innate skills or aptitudes to learn fast. So the results of the studies allow educators to know what is best and how to teach it, not forcing it, but to share most appropriately.