Answer: a) Calcium chloride : Compound
(b) Sulfur : Element
(c) Baking powder: Mixture
(d) Cytosine : Compound
Step-by-step explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions. Example: Sulphur (S)
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: calcium chloride
, Cytosine

Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present. Example: Baking powder which is made of tartaric acid and sodium bicarbonate.