To determine the correct total number from the options given, let's evaluate each statement:
Diabetes is primarily classified into two main types: Type 1 and Type 2. However, there is sometimes a mention of Gestational Diabetes, which occurs during pregnancy, making it sometimes seen as a third type. Therefore, saying there are 3 types is context-dependent but not entirely incorrect. However, it is not universally accepted in the medical community as strictly having three types.
Humans have 7 cervical vertebrae. This is a standard fact of human anatomy. Hence, the statement that there are 8 cervical vertebrae is incorrect.
Humans have 12 pairs of ribs. The last two pairs (11th and 12th) are known as floating ribs because they are not attached to the sternum directly or indirectly. So, there are indeed 4 floating ribs in humans (2 pairs), making this statement correct.
Proteins are composed of 20 different amino acids. Hence, the statement that there are 16 amino acids is incorrect.
Based on the analysis above, the only correct statement is: floating ribs in humans - 4. Therefore, the correct answer is:
Floating ribs in humans - 4