VKat, "claims to be" is certainly one correct form, and it's what we use in the correct answer here, so you know it's valid! However, there are other uses of the word "claim." As my colleague Ron (quoted by hazelnut above) points out, we can also say "claim that." We can also follow "claim" directly with a noun. Let's look at each form:
Claim [noun]: We are directly making a claim on something by saying that it is or should be ours.
To claim a prize, fill out this form.
Is someone going to claim this burrito, or should I throw it away?
Both sides claimed a victory in the debate last night.
Several Russian politicians claim a direct line of descent from the last tsar.
Claim to be: We are saying that we
are something. As with the verb "is," this can be followed by a noun or a modifier ("I am the king" or "I am tall"). In the original q, "able to assess" serves as a modifier.
My friend was scammed by someone on the phone claiming to be a Microsoft representative.
I don't claim to be beautiful, but I'm not frightening to look at.
My cousin claims to be able to solve a Rubik's Cube in 12 seconds.
Claim that: We are saying that some statement is true. The part after "that" should always be an independent clause.
Several companies claim that their patents were infringed by the new product.
He claimed that he would get the job done overnight, but I didn't believe him.
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