What do they mean by multi threading

To increase sales, robert sends out a newsletter to his customers each month, letting them know about new products and ways in which to use them. in order to protect his customers' privacy, he uses this field when addressing his e-mail. attach bcc forward to

The head restraint should be adjusted so that it reaches a. the top of your ears b. the base of your skull c. the top of the head

Me if you do then you get 10 points and brainliest