People are most successful at noticing an analogous relationship between problems if they focus on

The correct answer is "structural features".

Explanation:

The missing options of this question are:

structural features.

surface features.

mental sets.

operators.

The correct answer is "structural features".

Regarding problem-solving scenarios, structural features are defined as causal relationships involved in problem situations. According to the 1987 scientific article "Surface and structural similarity in analogical transfer" by Keith J. Holyoak & Kyunghee Koh, structural features have a greater impact on people's problem solver’s ability than surface features, which do not have a causal role.

allowed for the prediction of the properties of missing elements.