A child has built a large block structure in his Head Start center. He now places two blocks upright and tries to make a bridge across them using a third block. He selects a block of the wrong length to make the bridge, however, and his structure topples. He tries again and again with this block, always getting the same result. A teacher moves over to him and says, "What if you tried a different block? Which block would be the right length?" The child thinks about this question, selects a longer block, and successfully completes the bridge. This is a good example of a teacher intervening:

within the zone of proximal development.

Explanation:

According to Vygotsky, the zone of proximal development refers to the distance between the level of real development that an individual has (ability to solve problems alone) and the level of possible development of learning that that individual can achieve (ability to solve problems with help someone more competent).

In the question above, we can see an example of a teacher intervening in the development of a child within the zone of proximal development. This is because the child realized that he had a problem with the structure he was creating, however he did not have enough knowledge to identify what the problem was. The teacher, realizing this, gave only a hint of what was wrong, making the child take this information and develop his own knowledge, solving the problem alone.

b) the heart is a pump made of muscle and that is difficult to grow in the lab.