1. Sure. Here, take a look.

2. It's a picture of rocks, right?
3. Not only rocks, Tom! Look closer. There are eggs.
4. Wow, I can't believe it.
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Q1: What is the full form of "Not only rocks'? a or b?
a. They are not only rocks.
b. There are not only rocks.

Q2: Does 'rocks' mean big stones or small stones?

Q1 - "Sure" is certainly not a sentence. In informal, vernacular speech, we use it all the time, but it's a grammar shortcut. Otherwise, your sentences are grammatical.

The definition of a rock is usually a large mass of stone making up a cliff or an outcropping, etc. We tend to be imprecise and apply the word to anything larger than a pebble, though. It would be better usage to say "stones" if they're no bigger than eggs.

Either "they" or "there" is acceptable. I prefer "there" since we're referring to a picture, which is in a specific place, as in "over there". But, referring to a group of objects, "they" is used.

A1: The full form of "Not only rocks" would be option a. "They are not only rocks."

A2: The term "rocks" can refer to both big stones and small stones. It is a general term that encompasses various sizes and types of stones.

To get the answer to Q1, we can examine the given conversation between Tom and the other person. The phrase "Not only rocks" is used by Tom to emphasize that there is more to the picture than just rocks. Looking at the options, it appears that option a, "They are not only rocks," is the complete form of the phrase.

To answer Q2, we can refer to the conversation again. Tom mentions that there are eggs in the picture along with the rocks. Therefore, based on the given information, it is not specified whether the term "rocks" refers to big stones or small stones.