Which of the following tools is used to find bloodstains?A) microscope. B) chromatograph. C) chemicals. D) computer.

The best answer is “C.
Chemicals”.

A microscope is of little use for examining a
bloodstain.  The blood cells are broken down, and there is nothing in a swab of a stain
to visualize that would be helpful.

A chromatograph can be
useful, but is only rarely used, and never employed in the early stages of bloodstain
analysis.

The most useful immediate tests for identifying
bloodstains are various chemical tests, some of which are discussed
below.

Computers, while helpful for recording and sorting
information, are not in and of themselves used in blood stain
analysis.

Tests for bloodstains are classified in terms of
their specificity as follows:

Visual Test:  Does the stain
resemble dried blood?

Presumptive screening:  The scientist
uses chemicals that react with normal constituents of blood, such peroxidase enzymes. 
An example is the Kastle-Meyer test in which a drop of phenolphthalein is added to the
stain, followed by a drop of hydrogen peroxide.  If the stain is blood, it will contain
peroxidase and  cause the phenolphthalein to turn pink.  The Kastle-Meyer test and
others are explained in the first reference.

Confirmatory
tests:  These usually involve reacting the stain with chemicals that will cause
hemoglobin in the blood to crystallize.  The crystals are found by microscopic
examination.  True, this test uses the microscope, but not in a manner that would make
“microscope” the correct answer to your question.

Species
tests:  Once the presumptive and confirmatory tests are found to be positive (i.e. the
stain is definitely blood), it is necessary to prove human origin.  The species tests
make use of human antibodies that will react only with human antigens (such as human
hemoglobin).

A chromatograph is occasionally used to
examine a bloodstain.  Chromatography is a very sensitive laboratory technique for
detecting and identifying a vast array of chemicals in small concentration.  The
procedure allows identification of chemicals in the stain that are components of blood. 
As said above, however, the chromatograph is typically used neither early nor commonly
at all in bloodstain analysis.

The second reference is a
comprehensive PowerPoint presentation on bloodstain analysis.