How do you select a curve?

I've been sent some dxf files which I can view and i've worked out how to select a rectangle and move it.  clicking on a straight line selects it, but clicking on a curve doesn't.  Idiot newbie can someone tell now to select a circle or an object with some straight sides and some curved?

Thanks

Circles and arcs should be selectable the same way as straight lines. An object consisting of several elements can be selected by pulling up a window around them.
Maybe the layer of some elements is locked.

If I click on the curve I get a blue dot where i click if that means anything. How do I put a window round something and select whats inside?

Capture.PNG

I see how to use a window so now all the arc is in light blue, but also all the rectangles which i don't want.  The arc looks like its lots of individual points rather than a line so maybe thats why i cant click to select.  How do I unselect the rectangles without losing the curved shape?

Thanks

Nest_1-1.dxf

This is the actual file

The arcs indeed are a series of small single lines.
You can make a connected object by selecting the single lines you wish to unify by pulling up a window around them, then go to Tools - Polyline - Create Polyline from Existing Segments. If necessary, you can Explode that again.
You can deselect an already selected line by clicking on it again.

Pulling up a window from left to right selects only the objects within the window, whereas from right to left also selects those touched by the window.

That's great thanks