He's been project a for some time, and now he's available, and giving you the green light. But projects b and c have suddenly reentered the picture. Damn them and their temptations! You don't want a to know about b or c, because a may not be ok with your association with b. Or c. It may be best to come clean to a today, about b and c. You'll know his reaction asap through his body language.