Final answer:
The client with a carbon monoxide blood level of 12 is most likely to experience symptoms such as headache, dizziness, weakness, vomiting, chest pain, and confusion.
Step-by-step explanation:
Carbon monoxide (CO) is a poisonous gas that can cause harm to the body when breathed in at excessive levels. Symptoms of carbon monoxide poisoning are often described as "flu-like" and can include headache, dizziness, weakness, vomiting, chest pain, and confusion. In severe cases, loss of consciousness, arrhythmias, seizures, or death can occur.