Question

This cake is __________ (sweet) that one.
A. As sweet as
B. Sweeter than
C. The sweetest
D. Sweet

Answer 1

Hint:There are 3 types for adjectives that equate one thing to another. Positive, comparative and superlative are the three classes of adjectives. For distinction between two or more subjects or objects, the comparative and superlative degrees are used.
A phrase that applies to adjectives and adverbs is "Positive degree" The positive degree is said to be an adjective or adverb that does not allow a contrast. (In other words, the usual form of an adjective or adverb is the 'positive degree').

Complete answer:
Two nouns,' cake' and 'one', where 'one' is the pronoun for 'cake', are contrasted. The 'sweet' content of each of these cakes is equivalent, because the positive degree is the sentence. The term (sweet) in the bracket is a positive adjective, "as... as" is the expression needed in such a sentence.
Option A is also right, since the expression is of a positive comparative degree.
Option B is wrong because 'sweeter than' is of the comparative degree and a positive degree is necessary.
 As 'the sweetest' is of the superlative degree of contrast, alternative C is false.
Option D is false since no degree of comparison is indicated from the term alone.

Hence the correct answer is option A.

Note:To classify things/nouns/etc., the positive comparison/adjective degree is used but not for comparison.
The positive form is the adjective's base form. A greater degree of certain consistency is represented by the comparative form. The highest degree is represented by the superlative form.