In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.
The purpose of the testing phase of software development is not to (21) the absence of errors in the programs being tested, but rather to find as many errors as possible. This statement may seem to contradict one’s intuitive notion of a successful test of a piece of (22) ; however, a successful test is one in which errors have been found, net one in which no errors have been detected.
There are generally two kinds of testing method: human testing and machine testing. In most companies where systems are developed, the first testing that occurs is not machine testing, but rather the detection of errors through (23) , team efforts, referred to as walkthroughs and inspection. With these methods, the author of the program forms a group with others who represent programming expertise or who may be part of the project team.
After code has been subjected to the manual testing described above, it is then machine test- ed. Again, the test cases are designed to detect the (24) number of errors. Incremental or integration testing occurs subsequent to unit testing. This means combing modules with those that have already been unit tested. The incremental approach not only tests the (25) of each module, but also the "rippling effects" of errors, and the interfaces among modules.

A) personal B) machine C) manual D) tester