Fill in the blanks using correct tense forms :
Joe's cat _____ into the river yesterday.

In the given sentence "Joe's cat fell into the river yesterday," the correct tense form of the verb to fill in the blank is "fell."

The sentence is in the past tense and describes a completed action that happened yesterday. The simple past tense "fell" is the appropriate choice for this context.

The other options are not suitable for this sentence. Option B, "was falling," is in the past continuous tense and indicates an ongoing action, which is not the correct tense for a completed action in the past. Option C, "have fallen," is in the present perfect tense and does not match the past tense context of the sentence. Option D, "is falling," is in the present continuous tense and is not relevant to the past event described in the sentence.

Therefore, the correct answer is "fell" (Option A).