The correct Passive form of the given sentence is:

☀ He was seen stealing the cycle by me.

So, the correct passive form is: "He was seen stealing the cycle by me."

The other options and their explanations:

☀ The cycle was seen to be stolen by me.

• This option changes the meaning of the original sentence. It suggests that "the cycle" was seen to be in the process of being stolen, which is not the intended meaning.

☀ He was seen to be stealing the cycle by me.

• This option is in the passive voice, but it uses the continuous form "to be stealing," which doesn't match the simple past tense used in the original sentence. The correct passive form uses the base form "stealing" without "to be."

☀ He was seen to be stolen the cycle by me.

• This option is not grammatically correct. The verb "stolen" should be followed by "by" when used in the passive voice, not "to be."