Step 1: Eliminate two sequences immediately by checking their very first stage.
Inside a mosquito, sexual development can only begin once gametocytes taken up from human blood turn into gametes, that first step is always gametogony. Any sequence option that opens with "sporogony" or with "formation of oocyst" is starting at the wrong end of the cycle, since sporogony and oocyst formation both happen much later, so those two options are ruled out right away.
Step 2: Trace what happens right after gametogony.
Once male and female gametes have formed inside the mosquito gut, they must physically fuse. That fusion step is fertilization, producing a single zygote, so fertilization has to be the step right after gametogony.
Step 3: Follow the zygote's transformation.
The zygote does not sit still, it elongates into a motile, worm-shaped ookinete, which then bores through the mosquito's gut wall and settles under the outer gut lining, rounding up into a static oocyst. So ookinete and oocyst formation comes directly after fertilization, before anything else can happen.
Step 4: Identify what happens last, inside the oocyst.
Only once the oocyst is established does it undergo repeated internal division to release large numbers of thread-like sporozoites, a process called sporogony. These sporozoites then travel to the mosquito's salivary glands, ready for the next bite. Sporogony is therefore the final stage, not an early one.
Step 5: Assemble the full order.
Putting the four confirmed positions together gives: gametogony, then fertilization, then ookinete and oocyst formation, then sporogony.
Final Answer:
The correct sequence is gametogony, fertilization, formation of ookinete and oocyst, sporogony, option (3).