Which of the following funding sources is specifically aimed at helping early-stage startups?

Let's define each of the terms in the options as follows: 

1. Series Funding: A structured, multi-stage process where a startup company raises capital from investors through a series of funding rounds.
2. Angel Investment: An individual who provides capital to a budding business or businesses, including early startups, usually in exchange for convertible debt or ownership equity. 
3. Corporate bonds: Debt securities issued by companies to raise capital for various purposes, such as expansion or operational costs. When an investor buys a bond, they are lending money to the company and, in return, receive regular interest payments (coupons) and the return of the principal.
4. Initial Public Offering (IPO): An IPO (initial public offering) is the first time a business raises finance publicly. Before that, it can only use private investment.

The most suitable answer for "funding sources is specifically aimed at helping early-stage startups" is option B, 'angel investment'.