I do not know what your particular textbook says and you probably ought to look in it for the exact answer that you are expected to put on the exam.
To me, the disadvantages of productivity improvement are closely tied to the disadvantages of capitalism in general because capitalism and productivity improvement go hand in hand.
When productivity improves, people in that industry tend to lose their jobs. This is certainly a disadvantage. As productivity improves, there comes to be a race between firms to cut costs and gain profits. This leads, in the modern, world, to outsourcing. Outsourcing is certainly a problem for the people whose jobs are lost.
In business and management people are always trying to improve productivity. The increased levels of standard of living people are enjoying today as compared to the past it is because of productivity improvement.
Some people do fear that improvement in manpower productivity may lead to unemployment. However, the actual experience all over the world has been quite opposite. Increase in productivity of manpower by has always resulted in increasing employment in every economy across the world.
Productivity be definition getting more of goods and services we want from per unit of input resources we have. This means productivity improvement helps us to get more of what we want. This can never be undesirable or disadvantageous.