Some toxic chemicals
a) can be assimilated directly through the skin unless proper protection is taken
b) can be ingested by transferance from hand to mouth after leaving the laboratory
c) can be inhaled even if the substance has a very high boiling point
d) all of the above

D) All of the above

Explanation:

Toxic chemicals are substances that can cause damage to human health or even death. However, some of these substances are useful for many proposers, like benzene, which is an important solvent.

So, in a chemistry lab, toxic chemicals are used or produced. To avoid contamination, some rules have to be followed. One of these rules is to use the appropriate safety equipment: coat, mask, and gloves, for example.

There are many ways these chemicals can enter the human body: in contact with the skin, ingested, in contact with the eyes and inhaled. Even if the substance has a very high boiling point, it can be inhaled, because some substances can give off gases and during a day lab, it's possible to achieve the boiling point too.

So, all the alternatives have ways to contamination.