question: How is the Knowledge Vault constructed? option 1: By extracting facts from web sources and evaluating their confidence. option 2: By training an SRL model on Freebase to predict link probabilities. option 3: By combining latent and observable models for link prediction. option 4: By using the ER-MLP model as a latent feature model. option 5: By applying the PRA approach to a subset of Freebase. 