In which of the following scenarios was service not proper?

Select one:

a.ABC Corp. is a corporation incorporated in Delaware. Personal service of the summons and complaint was made on the CEO.

b.ABC Corp. is a corporation incorporated in Delaware. Personal service was made on the personal assistant to the CFO, who is authorized to receive service.

c.ABC Corp. is a corporation incorporated in Delaware. Service was made by delivering a copy of the summons and complaint to one of ABC Corp.'s managers in a retail store in California.

d.ABC Corp. is a corporation incorporated in Delaware. Delaware law allows for service to be made on a corporation by printing an ad in the local newspaper. The summons and complaint are printed in the local Sunday paper.