Select all the true statements:

1.Clustering algorithms generally seek to group together entities that are the least dissimilar according to a provided dissimilarity metric.

2.Clustering and PCA are both used for regression problems.

3.PLS seeks a projection of features to a lower dimensional space such that the lower dimensional projected features is as good as possible at predicting a target.

4.PCA seeks a projection of variables to a lower-dimensional space in a way that preserves as much variation in the data as possible.