# import necessary libraries
import pandas as pd
import numpy as np

# create a 2D NumPy array
arr = np.array([[1, 2], [3, 4]])

# transpose the NumPy array
arr_transposed = arr.T

# convert the NumPy array to a Pandas dataframe
df = pd.DataFrame(arr_transposed, columns=['A', 'B'],
                  index = ['row1', 'row2'])

# print the dataframe
print(df)