The writer prefers to use the word chalkboard rather than blackboard because
Directions: Read the passage and answer the given question.
(This article was written in the late 20th century)
The chalkboard is by far the commonest teaching aid used at virtually all levels of education from the nursery to the university. It is the most enduring teaching aid and perhaps will be the most difficult to replace. In the advanced countries of the world, it is being threatened by the overhead projector However, the overhead projector requires constant supply of electricity - which is one reason we cannot rely on it yet. The chalkboard used to be black, that was why the name "blackboard" stuck for ages; but today, there are boards of various colours: blue, green, even white.
Now, most chalkboards are made of wood nailed to the wall, instead of the concrete board made of cement and fine sand that was more common. Some are also made of metal. The chalkboard has the advantages of low cost, availability and ease of maintenance, usually involving mere cleaning and occasional retouching of the surface with the renovator. However, if the board is metal, the felt marker should be protected against drying by replacing the cap when it is not in use. The major drawback in the use of the chalkboard is that the information on it can only be temporary. If there is only one board for the class, it is usually impossible to leave the information there for more than a few hours, since other teachers would want to use it.
It is not easy to draw complex diagrams showing minute details, such as parts of the body and contours, unless one is a good artist. Where one has succeeded with the laborious illustrations, using different colours, it could be painful when the board has to be cleaned by the next teacher. However, there are nowadays various innovations, including foldable boards made of plywood, which allow teachers more room to leave their materials for longer periods.
Finally, it is a great disadvantage that during the course of teaching, much time is spent in writing on the board than when one is using the overhead projector. So, in all, more time is needed for any lesson when one uses the board rather than the overhead projector.