Enginpasa1 wrote:in regards to CR, I have a weakness in Assumptions and Inferences. Is there non-OG place, book or online resource that I can do some exercises?

you could try manhattangmat's critical reasoning strategy guide, which contains, inter alia, a chapter on the different types of assumptions that often appear in cr problems.

here's a helpful hint from my own tortured brain:
i find that making 'flowchart'-style diagrams - with assertions in little boxes, and arrows between the boxes to show logical progression - is extremely helpful in elucidating the logic of CR problems. once you make such a diagram, think about each arrow in turn, and decide whether any of the arrows represents a deduction that rests upon questionable assumptions.

for instance, in this problem, i would diagram the environmentalist's statement as follows:
box containing 'photographs would damage public image'
...arrow to ...
box containing 'damaged public image lowers sales'
...arrow to ...
box containing 'lower sales = concern'
...arrow to ...
'no other concern'
in this mini-diagram, the first two arrows represent sound reasoning, but the third arrow is highly questionable: that the company has concern X does not, in any way, imply that it has no other concerns. it is clear, then, that more than one assumption is at work here.

hope that sort of approach helps.