a) <datalist>
b) <keygen>
c) <output>
d) <password>

Answer: a
Explanation: The datalist tag is used to provide an “autocomplete” feature on input elements. Users will see a drop-down list of pre-defined options as they input data. Password defines password field in HTML. It is attribute for input-type. The <keygen> element references from data after form has submitted. Result of calculation (script) is represented by output tag.