$($d$)$ Which of the following techniques can be categorised as unsupervised learning?A$.$ k$-$nearest neighbour.B$.$ Back$-$propagation neural network.C$.$ Simulated annealing.D$.$ Hierarchical clustering.E$.$ k$-$means clustering.F$.$ A single perceptron.G$.$ Self$-$organising feature map $($SOM$).$