How can Clustering (Unsupervised Learning) be used to improve the accuracy of Linear Regression model (Supervised Learning): 1. Creating different models for different cluster groups. 2. Creating an input feature for cluster ids as an ordinal variable. 3. Creating an input feature for cluster centroids as a continuous variable. 4. Creating an input feature for cluster size as a continuous variable. Options: A. 1 only B. 1 and 2 C. 1 and 4 D. 3 only E. 2 and 4 F. All of the above