The answer is "it leaves things uncertain."
This passage focuses on the mother's understanding; it does not focus on Imogen's inner thoughts or her love for the children.
However, it does not specifically explain the "many things" the mother thought when she looked away from her child's eyes. Therefore, it leaves these things uncertain.
The correct answer that would best complete the given statement above would be the term SATIRE. In "They,” Sassoon uses the literary technique of SATIRE, which attempts to mock others with irony. This is a literary technique used by writers to criticize f<span>oolishness and corruption of an individual or a society by using humor, irony, exaggeration or ridicule. Hope this answer helps.</span>