Free birth is an suspected requirement for membership in the blue vein society. Option A is the correct.
If you look up the word allege in the dictionary, you will find that it is said, without proof, to have taken place or to have a specified illegal or undesirable quality.
What is more, the word suspected is considered one of the synonyms of the word alleged, along with so-called, claimed, professed, purported, ostensible, apparent, putative, unproven,