I. Some tools are useful: This follows because all gadgets are machines, and some gadgets are tools. Since all machines are useful, some tools are useful.
II. All that is useful are machines: This does not follow because being useful does not necessarily mean it’s a machine.
III. All tools are gadgets: This does not follow as the relationship between tools and gadgets is only partial (some gadgets are tools).
Thus, the correct answer is Option (A).