Final answer:
The word 'suggestion' is the closest synonym for 'trial' as a noun.
Step-by-step explanation:
The word 'trial' as a noun can be synonymous with several words depending on its context, but in the choices provided, the word suggestion is the closest in meaning to 'trial'. Hypothesis is another term that aligns closely with 'trial' and 'suggestion', as it refers to a proposed explanation for a phenomenon that one can test through experimentation and observation. The word 'trial' suggests an attempt to discover something or to test a hypothesis; similarly, a hypothesis is a tentative idea or suggestion that one tests through scientific methods.