The options A, B and D are all difficult to determine given the difference in side lengths. Option C is definitely an isosceles triangle because it has two sides equal.
Two of its sides measure 4.7 cm each (which is one of the properties of an isosceles triangle).
Ideally all other options have three sides given, but in view of the question the best option is C, since its already been defined as an isosceles due to the dimensions given.