Why in general do financial managers make financial decisions in a corporation, rather than the owners making these decisions themselves?

Finance managers can handle surround limitations along with profit maximization. 

in general , financial managers do not make financial decisions rather they give thier contributions or suggestions then the company with other company's manager will deliberate and come to a conclusion.

Finance Managers are hired through the extensive screening process and they are expected to be an independent and highly skilled professional executors. The owners appoint them to take perfect decisions based on their qualification and the experience. 

Well, in general, applicable to all types of organization, Finance Managers take the decisions but he/she has to take consultation and get the owner or the representative of the owner (Director or the MD) well informed. Being that, the owners of the public company appoint the management committee who has to perform for their profit maximization and the organizational wel-being, the financial managers are basically delegated to take decisions within a certain standard. 

Lets consider an example; when a company declares not to declare dividend this year but take a major project investment then, the basic root of the decision will have been priorly suggested by the finance manager but he alone wouldn't be authorized to make that investment decision without the dividend addressed to the owners which is always been expected. It is the decision sanctioned through the general meeting. The budget for the coming financial year is allocated and that portion of financial resource is what the finance manager does his part.

Summary: Finance Managers do not actually, in general make financial decisions in a corporation. It is always an act of coordination among different depart heads. He/She has to work under the General Manager and is subject to controlling and make suggestions on the financial affairs, and only permitted with a decision making up to the constraint served. This is a vast issue. I could write an article for this.. haha!

Thanks for the question.

The answer is D. 

Ownership changes every time with buying and selling the stocks 

There are often many owners, and they can often change as they buy and sell stock

It is best for the control of the finance to be in the hands of those who are independent to company's financial status. Also not necessarily that the corporation owners are finance specialists to direct the company's financial direction in an appropriate way.