Occasionally, the 副助詞（ふくじょし） (adverbial particle) ばかり is combined with verbs in their 連体形（れんたいけい） (attributive form), to show that (A) is the only thing that is occuring. It may also imply that (A) is happening ‘more and more’, or that ‘it keeps on (A)’. This phrase utilizes ばかり’s standard meaning of ‘only’, and combines it with the 助動詞（じょどうし） (auxiliary verb) だ (or です).

• ガソリンの値段（ねだん）は上（あ）がっていくばかりだ。
  The price of gas keeps rising.
• 最近（さいきん）は全然（ぜんぜん）体（からだ）を鍛（きた）えていないから、筋肉（きんにく）がなくなっていくばかりだ。
  Recently I haven't been working out, so I keep on losing muscle.
• 日本（にほん）の人口（じんこう）は減（へ）るばかりです。
  Japan's population continues to drop.
• この辺（へん）は犯罪（はんざい）が多（おお）いので、治安（ちあん）が悪（わる）くなるばかりです。
  Because there are so many crimes around here, the public safety of the area continues to get worse.

As can be seen with these sentences, this use of ばかり is paired almost exclusively with verbs that describe some form of change (higher/lower, stronger/weaker, better/worse, faster/slower, etc).
If the speaker would like to express further information in a (B) part of the sentence, だ will simply get changed to its 連用形（れんようけい） (conjunctive form) で, before continuing.

• この町（まち）の治安（ちあん）が悪（わる）くなるばかりで、しばらく良（よ）くなりそうもない。
  The reputation of this town keeps on getting worse, and it doesn't look like it will get better anytime soon.
• 観光客（かんこうきゃく）が減（へ）るばかりで、周（まわり）りの店（みせ）が潰（つぶ）れていっている。
  The amount of tourists keeps on dropping, and the stores around us are closing.