Consider the following variables in Python:
a1 = np.random.rand(4)
a2 = np.random.rand(4, 1)
a3 = np.array([[1, 2, 3, 4]])
a4 = np.arange(1, 4, 1)
a5 = np.linspace(1 ,4, 4)
Which of the following statements regarding these variables is correct?
A. a3.shape == a4.shape
B. a4.ndim() == 1
C. a5.shape == a1.shape
D. a1.shape == a2.shape