Limits to variation The most obvious limit to natural selection is that suitable variation may not be available. This may be because certain phenotypes cannot be built, being ruled out either by physical law or by the properties of biological materials.
<h2>Answer:</h2><h3>1. Hepatitis B </h3><h3>2. Levels of circulating antibodies against a certain antigen.</h3><h2>Explanation:</h2><h3>Hope its help</h3>
