Answer:
A - Abstruse: difficult to understand; obscure.
Sentence: The abstruse concept of quantum mechanics can be challenging to grasp.
B - Baleful: threatening or harmful in intent or effect.
Sentence: The baleful glare from his boss made him nervous.
C - Capricious: given to sudden and unaccountable changes of mood or behavior.
Sentence: Her capricious personality made it hard for others to predict her actions.
D - Desultory: lacking a plan, purpose, or enthusiasm.
Sentence: He made a desultory attempt at studying for his exam, resulting in a poor grade.
E - Ebullient: cheerful and full of energy.
Sentence: The ebullient children were laughing and playing in the park.
F - Furtive: attempting to avoid notice or attention, typically because of guilt or a belief that discovery would lead to trouble.
Sentence: He cast a furtive glance around the room, hoping no one would see him.
G - Garrulous: excessively or pointlessly talkative.
Sentence: The garrulous professor went on and on about his research, leaving his students bored.
H - Hapless: unfortunate and deserving of pity.
Sentence: The hapless victim of the accident was rushed to the hospital.
I - Ineffable: too great or extreme to be expressed or described in words.
Sentence: The beauty of the sunset was ineffable, leaving the onlookers speechless.
J - Jocular: fond of or characterized by joking; humorous or playful.
Sentence: His jocular personality made him a hit at parties.
K - Knavish: dishonest; untrustworthy.
Sentence: The knavish salesman tried to cheat his customers out of their money.
L - Lugubrious: looking or sounding sad and dismal.
Sentence: The lugubrious music played at the funeral made everyone feel even more sorrowful.
M - Mellifluous: sweet-sounding; pleasing to the ear.
Sentence: The mellifluous voice of the singer made the audience feel entranced.
N - Nefarious: wicked or criminal.
Sentence: The nefarious plot to rob the bank was foiled by the police.
O - Obdurate: stubbornly refusing to change one's opinion or course of action.
Sentence: The obdurate employee refused to take his boss's advice, even though it would have helped the company.
P - Pernicious: having a harmful effect, especially in a gradual or subtle way.
Sentence: The pernicious habit of smoking eventually led to his lung cancer.
Q - Querulous: complaining in a petulant or whining manner.
Sentence: The querulous customer demanded to speak to the manager, even though the problem had already been resolved.
R - Risible: such as to provoke laughter; ludicrous.
Sentence: His risible attempt at a joke fell flat, leaving everyone awkwardly silent.
S - Sanguine: optimistic or positive, especially in an apparently bad or difficult situation.
Sentence: Despite the setback, she remained sanguine about the future.
T - Tenebrous: dark and gloomy.
Sentence: The tenebrous atmosphere of the abandoned house made her shiver.
U - Ubiquitous: present, appearing, or found everywhere.
Sentence: The ubiquitous nature of social media makes it difficult to avoid.
V - Vexatious: causing annoyance, frustration, or worry.
Sentence: The vexatious problem with the computer kept him from finishing his work.
W - Welter: a large number of items in no order; a confused mass.
Sentence: The welter of papers on his desk made it hard to find what he was looking for.
X - Xenial: hospitable, especially to visiting strangers or foreigners.
Sentence: The xenial host welcomed the guests with open arms.
Y - Yearning: a feeling of intense longing for something.
Sentence: His yearning for a better life motivated him to work harder.
Z - Zealous: having or showing great enthusiasm or devotion.
Sentence: The zealous fan of the band had been following them on tour for weeks.
Here are some example sentences that use all four types of sentences:
Declarative: The sun is shining brightly today.
Interrogative: Is it going to rain later?
Imperative: Please pass the salt.
Exclamatory: What a beautiful day it is!