[单选题]BF004母锥是长筒性整体结构，由接头与本体两部分构成，接头上有正、反扣标志槽，本体内锥面上有打捞螺纹，打捞螺纹与公锥相同，有(　)及89030，两种。同时也分有排屑槽和无排屑槽两种。
A.60°
B.30°
C.55°
D.65°

[A] The petitioners argue that repealing the tax will cost the Treasury billions of dollars in lost revenues and will result in either increased taxes in the long run or cuts to Medicare, Social Security, environmental protection and other government programs. Repealing the levy "would enrich the heirs of America’s millionaires and billionaires, while hurting families who struggle to make ends meet," the petition says.
[B] About 120 wealthy Americans had signed or supported a petition to oppose phasing out the tax. President Bush has included the repeal of the tax in his $1.6 trillion tax-cut proposal. Normally when "dozens" of Americans join in a political cause, it is not particularly noteworthy, but in this case the dozens include: George Soros, a billionaire financier; Warren Buffett, an investor listed as America’s fourth-richest person; the philanthropist David Rockefeller Jr. ; and William Gates Sr. , a Seattle lawyer and father of A