An exclamatory sentence is a type of sentence that conveys strong emotions, such as surprise, joy, sorrow, or excitement. In this case, the original assertive sentence is "It is sad that we lost the match." To transform it into an exclamatory sentence, we need to express strong emotion.

Option (3) "Alas! We lost the match." is the correct choice because it conveys a strong feeling of sorrow or regret. "Alas" is an interjection often used to express regret or disappointment, making it suitable for an exclamatory sentence.

The other options do not effectively express strong emotions or are not structured as exclamatory sentences. For example, option (1) begins with "How sad," but it does not form a complete exclamatory sentence. Option (2) lacks the emotional intensity expected in an exclamatory sentence, and option (4) introduces the word "Oh" to express emotion but does not use it in a manner typical of exclamatory sentences.

Therefore, option (3) is the correct choice for an exclamatory form of the given assertive sentence.