'Joyful' is a synonym of 'happy'.

'Tall' describes the noun 'building', making it an adjective.

Tall describes the noun 'building' and is therefore an adjective.

'Pessimistic' means having a negative outlook, which is the opposite of 'optimistic'.

'Opaque' means not able to be seen through, so 'transparent' is the opposite.

'Kind' is closest in meaning to 'benevolent', which refers to being well-meaning and kindly.

'Ephemeral' means lasting for a very short time, similar to 'transitory'.

'Constraint' is synonymous with 'limitation', as both refer to restrictions.

'Kind' is synonymous with 'benevolent', which means showing goodwill.

'Seperate' is spelled incorrectly; the correct spelling is 'separate'.

'Elated' means very happy or proud; therefore, the synonym is 'joyful'.

'Meticulous' means showing great attention to detail, making 'thorough' the correct synonym.

'Descend' means to go down, which is the opposite of 'ascend'.

'Simple' is the antonym of 'difficult', indicating ease.

'Contract' means to become smaller, which is the opposite of 'expand'.

'Rare' is the antonym of 'frequent', indicating something that does not happen often.

'Selfish' is the antonym of 'generous', indicating a lack of willingness to share.

'Heavy' is the opposite of 'light'.

'Quiet' is the antonym of 'noisy', meaning making little or no sound.

'Pessimistic' is the antonym of 'optimistic', which refers to a tendency to see the worst aspect of things.

'Complicated' is the opposite of 'simple'.

'Failure' is the opposite of 'success', indicating a lack of achievement.

'Fish' is an aquatic animal, while the others are terrestrial.

'Car' is not an animal, while the others are all pets.

'Contract' is the opposite of 'expand', meaning to decrease in size.

'Plentiful' means existing in large quantities, which is synonymous with 'abundant'.

'Reduce' means to make smaller or less, which is synonymous with 'diminish'.

'Hasten' means to speed up, which is the same as expedite.

'Thorough' is a synonym of 'meticulous', meaning showing great attention to detail.

'Mitigate' means to make something less severe, serious, or painful.