What does もとになる mean here?


This is from the 日本能力試験直前対策N3 book, page 36.

> このマークは、区長が親しみやすさと、あたたかさを感じさせるものにしたいと考えて **もとになる** アイディアを出し、A市に住むデザイナーに頼んで作った

Usually when I see sentences with もとになる it has the form "Noun+のもとになる" meaning
on the basis of Noun. But there is nothing before もとになる here.

Also, unrelated, but can you omit このマークは and have the meaning not change
because it is not the subject of the sentence? In other words, is it not
attached to any verb or predicate in the sentence just like "As for the mark"
would not be in the English translation?




It's **マークの** もとになる ("which works as the basis **of the mark** "), but マークの is
not explicitly mentioned here because it has been already mentioned as the
topic of the sentence. So the 区長 created the basic idea and a professional
designer finalized it.

Generally speaking, you can omit the wa-marked topic if it can be inferred
from the context. I cannot say yes or no for this specific sentence because
you have not provided the previous context.




It's **マークの** もとになる ("which works as the basis **of the mark** "), but マークの is
not explicitly mentioned here because it has been already mentioned as the
topic of the sentence. So the 区長 created the basic idea and a professional
designer finalized it.

Generally speaking, you can omit the wa-marked topic if it can be inferred
from the context. I cannot say yes or no for this specific sentence because
you have not provided the previous context.

