Final answer:
Deep learning is a part of machine learning characterized by the use of multi-layer neural networks. The correct answer is option c) A form of machine learning that involves complex, multi-layer neural networks.
Step-by-step explanation:
Deep learning is best described as a form of machine learning that involves complex, multi-layer neural networks, which makes option c the correct answer. Unlike regression analysis that focuses on predicting a quantitative response, deep learning is capable of automatically discovering patterns and features in data. There are distinct forms of machine learning, such as reinforcement learning, but deep learning specifically relies on layered structures known as artificial neural networks with often many hidden layers between the input and output, hence the term 'deep'.
In contrast to option d, while deep learning uses 'hidden' layers, the term 'hidden' simply means that these layers are not input or output layers but intermediate layers—this characteristic is true for many neural network architectures, not just deep ones.
Furthermore, while classical and Pavlovian conditioning are indeed forms of associative learning, they are unrelated to the intricate computational models used in deep learning.