执行下面代码段,对其输出结果描述正确的是_______。import tensorflow as tfmnist = tf.keras.datasets.mnist(train_x, train_y), (test_x, test_y) = mnist.load_data()print("training set:", train_x.shape)print("testing set:", len(test_x))
A.
training set:(60000,) testing set:10000
B.
training set: (60000, 28, 28) testing set: 10000
C.
training set:(10000, 28, 28) testing set: 60000
D.
training set:(10000,) testing set: 60000