Option B has the incorrectly spelt word. The correct spelling is "referendum" which means a direct vote in which an entire electorate is invited to vote on a particular proposal. The meanings of the other words are:

Treachery = betrayal of trust.

Suppression = to end something by force

Resemblance = the state of resembling or being alike

Option C has the correctly spelt word. ‘Schemata’ means ‘a plan in the form of a mode.’ The correct spelling of the other words along with their meaning are: 

Deceased ⇒ dead 

Speedier ⇒ faster 

Unionist ⇒ a member of a trade union.

The correctly spelt word is actuation. Actuation means to incite or move to action; impel; motivate. 

Hence, option D is the correct answer.

Option B has the incorrectly spelt word. Its correct spelling is "Coefficient" which means a numerical or constant quantity placed before and multiplying the variable in an algebraic expression. The meanings of the other words are:

Coalition = the joining together of different political parties or groups for a particular purpose

Classification = the act or process of dividing things into groups according to their type

Option D has the incorrectly spelt word. Its correct spelling is ‘annual’ which means occurring once a year. 

Sylabus is the incorrect spelling of syllabus which means the subjects in a course of study or teaching. 

Coalesse is the incorrect spelling of coalesce which means to come together to form one mass or whole. 

Adhetion is the incorrect spelling of adhesion which is the action or process of adhering to a surface or object. 

Encroach is the correct spelling which means to intrude on (a person's territory, rights, personal life, etc.). 

Hence, option B is the correct answer.

Option D has the misspelt word. Its correct spelling is "piety" which means the quality of being religious or reverent. The meanings of the other words are:

Anxiety is a feeling of worry, nervousness, or unease about something with an uncertain outcome. 

Believe means to accept that (something) is true, especially without proof. 

Height is the measurement of someone or something from head to foot or from base to top.

Uncanny is the correct spelling. It means strange or mysterious, especially in an unsettling way.

Sorrow is the correct spelling. It means a feeling of deep distress caused by loss, disappointment, or other misfortune suffered by oneself or others.

Billowy is the correct spelling. It means characterized by great swelling waves or surges.

Cravrat is the incorrect spelling of Cravat. It is a short, wide strip of fabric worn by men around the neck and tucked inside an open-necked shirt.

Option C has the correctly spelt word. Piquancy means a pleasantly sharp and appetizing flavour.

Metalled/Metaled = any of a class of elementary substances, as gold, silver, or copper, all of which are crystalline when solid

Lonesome = depressed or sad because of the lack of friends, companionship

Shuffled = past of "shuffle" means walk by dragging one's feet along or without lifting them fully from the ground.

Spliter is the incorrect spelling of splinter which is a small, thin, sharp piece of wood, glass, or similar material broken off from a larger piece. 

Palenes is the incorrect spelling of paleness which is an unusual lightness of skin colour as compared to your normal complexion. 

Bloting is the incorrect spelling of bloating which means to make or become swollen with fluid or gas. 

Pillages is the correct spelling which means to rob a (place) using violence, especially in wartime. 

Hence, option A is the correct option.