cottoning怎么读

vi.喜欢（cotton的现在分词形式）...

By now the students seemed to be cottoning on.学生们忽然明白了什么.He seems to be very slow cottoning to the significance of the new method.他似乎对新方法的重要意义迟迟不能理解.Still, last year's figures may be a sign that Europe is cottoning ...