执行下列程序段，结果为______。 
import tensorflow as tf
x = tf.Variable(tf.constant([5, 6, 7]))
x.assign([1, 2, 3])
x.assign_add([3, 2, 1])
print(x.numpy())
print(x.trainable)
A、[4 4 4]
True
B、[8 8 8]
True
C、[8 8 8]
报错
D、[4 4 4]
报错