Final answer:
The synonym for 'fathom' in the sentence is 'Understand.' 'Fathom' means to grasp or comprehend something, making 'Understand' the correct choice. Option a.
Step-by-step explanation:
In the context of the sentence provided, the correct synonym for the word fathom is option a) Understand. The word 'fathom' means to comprehend or grasp something, often something difficult to understand. Therefore, the closest synonym from the options given is 'Understand.'
Ignore, option b), has the opposite meaning as it refers to not considering something or deliberately paying no attention to it. Confuse, option c), means to make something unclear or difficult to understand, which is also contrary to the meaning of 'fathom.'
Option d) Multiply has no relation to understanding or comprehension and is instead a mathematical term that means to increase or add something in number.
So option a.