A weak acid is best described as

[monokekie]

A weak acid is best described as one that:

A contains a low concentration of an acid.
B has a pH only slightly less than 7.
c is only partially ionised in aqueous solution.
D reacts slowly with magnesium ribbon.

I encountered a bit of a dilemma in picking the correct answer.
any suggestion would be appreciated 

[/0]

A is irrelevant.
For B you can have 0.00000000001M HCl and it will have a pH only slightly less than 7, not the best description.
D also depends on the concentration.

Hence, C

[lukeperry91]

Under the Bronsted-Lowry model an acid is a substance that will donate a H molecule, and the degree of the willingness to donate is the strength.
As /0 said, concentration is irrespective of the strength of an acid or base.
From wikipedia: "Magnesium also reacts exothermically with most acids, such as hydrochloric acid (HCl)"
The rate at which it reacts is dependent upon the concentration, not the strength, as a higher concentration will induce a net forward reaction which you should remember from studying Le Chat's Principle. A stronger acid will contribute to a higher equilibrium yield as more activation complexes are likely to form. A classic yield vs. rate question

[TrueTears]

Yeah just remember the strength of an acid or base is its ability to ionise in water.

[monokekie]

arh alrite, thanks 0/, lukeperry and TT !!!