下面的一段python程序是对iris数据集进行训练集和测试集的拆分，已知该数据集中样本的个数为150个，特征为4个。则下面的程序执行完毕后，print语句的输出结果应改为： from sklearn import datasets from sklearn.model_selection import train_test_split iris = datasets.load_iris() X_train, X_test, y_train, y_test = train_test_split(iris.data, iris.target, test_size=0.3) print("X_train.shape: ", X_train.shape, "y_train.shape: ", y_train.shape)
选项：

A:X_train.shape: (150,4) y_train.shape: (150,)
B:X_train.shape: (105,4) y_train.shape: (105,)
C:X_train.shape: (45,4) y_train.shape: (45,)
D:X_train.shape: (120,4) y_train.shape: (120,)