law definition needed to be explained

Mere silence as to facts likely to affect the willingness of a person to enter into a contract is not fraud, unless the circumstances of the case are such that, regard being had to them, it is the duty of the person keeping silence to speak2, or unless his silence, is, in itself, equivalent to speech.
(a) A sells, by auction, to B, a horse which A knows to be unsound. A says nothing to B about the horse’s unsoundness. This is not fraud in A. (a) A sells, by auction, to B, a horse which A knows to be unsound. A says nothing to B about the horse’s unsoundness. This is not fraud in A."
(b) B is A’s daughter and has just come of age. Here the relation between the parties would make it A’s duty to tell B if the horse is unsound. (b) B is A’s daughter and has just come of age. Here the relation between the parties would make it A’s duty to tell B if the horse is unsound."
(c) B says to A—‘‘If you do not deny it, I shall assume that the horse is sound”. A says nothing. Here, A’s silence is equivalent to speech. (c) B says to A—‘‘If you do not deny it, I shall assume that the horse is sound”. A says nothing. Here, A’s silence is equivalent to speech."
(d) A and B, being traders, enter upon a contract. A has private information of a change in prices which would affect B’s willingness to proceed with the contract. A is not bound to inform B. (d) A and B, being traders, enter upon a contract. A has private information of a change in prices which would affect B’s willingness to proceed with the contract. A is not bound to inform B."

can any 1 please explain what does the definition say i am not getting it
especially that "regard being had to them"
help would be really apprieciated