Final answer:
The word that is a synonym for "tremble" when used as a noun is 'shiver'. Students are also asked to underline the letter 'b' in a list of given words to recognize its presence.
Step-by-step explanation:
The student has asked for a synonym for "tremble" when used as a noun. Among the options given (venture, streamlet, impost, and shiver), the correct synonym for "tremble" is d) Shiver. This is because both words refer to a shaking or quivering movement which can be due to cold, fear, or another intense emotion.
Now, regarding the exercise to underline the letters that spell b in various words, we can do this as follows: able (b), scrible (b), resemble (b), pebble (b), tremble (b), noble (b), gamble (b), bubble (b).