あのレコードがあったら＿＿＿＿＿買（か）います。
a. たかいが
b. たかいけど
c. たかいのに
d. たかくても

Today’s topic is an adversative conjunction, [てform]+も, which is usually translated as “even if”.

All of the above choices include an adversative conjunction (a conjunction that connects contrasting/opposite parts) but in this example only d. たかくても can be used.

Why?

あのレコードがあったら、高くても買います means “If (a shop) has that record, I will buy it even if it’s expensive.” In this situation, the record being expensive is only an assumption, not a fact, because あのレコードがあったら suggests that they (shop) may not have it, and [てform]+も is the only one here which can be used with an assumption.

Some more examples of similar use:

<verb>
あめがふっても、10キロはしる。
Even if it rains, I will run 10 km.

さがしてもみつからないだろう。
Even if you look for it, you won’t find it.

みつからなくても しかたがない。
It can’t be helped even if it is not found.

<いadjective>
むずかしくても がんばる。
I’ll do my best even if it is difficult.

おいしくなくても たべる。
I’ll eat it even if it is not delicious.

<なadjective>
さしみは しんせんでも たべない。
Even if sashimi is fresh, I won’t eat it.

まじめじゃなくても だいじょうぶです。
It is OK even if he is not studious.

If the sentence did not have あのレコードがあったら, all other 3 sentences make sense and they mean:
a. たかいが 買（か）います。It is expensive but I will buy it.
b. たかいけど 買（か）います。Although it is expensive, I will buy it (almost the same with the above)
c. たかいのに 買（か）います。Even though it is expensive, I will buy it. (not much difference from the above 2)