Which sentence does not have an error in subject and verb agreement?

a.
glimmering sun and crashing surf has a soothing effect on me.

b.
a piece of cake with a candle was brought to my table on my birthday.

c.
the curtains, soft and white, was billowing in the breeze.

d.
isn't basil and thyme two herbs you use in your sauce?

Wow... I can see how these are tricky. It all comes down to [like the question asks] grammar.

(a) should be correctly written as 
"Glimmering sun and crashing surf has a soothing affect on me.
(NOT effect)

(b) ... this is just a run-on. too many errors in this one.

(c) should be
"the Curtains, soft and white, were billowing in the breeze.
(NOT was- this is the wrong past tense)

(d) This one seems to be the best answer...

Good luck!