Question

form a compound sentence.
all water buffalo have

horns, but the females horns are smaller than the males
backward - curving horns with deep ridges on their surfaces
wide, hoofed feet and carry ridged, backward - curving horns

Explanation:

To form a compound sentence, we need to combine two independent clauses. The first part "All water buffalo have" needs a phrase that can be part of a clause, and then we can use a conjunction (like "and") or another way to connect. Wait, actually, looking at the options, the correct completion should be a part that when added to "All water buffalo have" forms a clause, and then we can have another clause. Wait, no, the first option is a compound sentence itself? Wait, no, the task is to form a compound sentence by filling in the blank. Let's analyze each option:

Option 1: "horns, but the females' horns are smaller than the males'" – If we put this in the blank, the sentence becomes "All water buffalo have horns, but the females' horns are smaller than the males'". This is a compound sentence with two independent clauses ("All water buffalo have horns" and "the females' horns are smaller than the males'") connected by "but".

Option 2: "backward - curving horns with deep ridges on their surfaces" – This would make a simple sentence: "All water buffalo have backward - curving horns with deep ridges on their surfaces", not a compound sentence.

Option 3: "wide, hoofed feet and carry ridged, backward - curving horns" – The structure "All water buffalo have wide, hoofed feet and carry ridged, backward - curving horns" is a simple sentence with a compound verb ("have" and "carry"), not a compound sentence.

So the correct option is the first one as it forms a compound sentence with two independent clauses connected by "but".

Answer:

horns, but the females' horns are smaller than the males'