Is this below example an invalid argument?

A ←S→ B -M→ C

__________

A ←S→ C

If so, can someone please explain why this form is invalid? Thanks in advance!

Is the explanation that '←S→' is implied within 'All' and we already know that 'all' cannot proceed '-M→' or ' ←S→'. If it does proceed either of those two quantifiers, the argument is invalid, is my basic understanding.

I got this wrong, but I don't know how else (other than the usual practice/takes more time trope) to change my reasoning. I was able to POE many of the answers, except for A. I eliminated D, correctly assuming that the public's attention is something journalist wanted. But for the previous portion of the answer, "A basic principle of journalism etc" , I felt thought the best way for a journalistc to stimulate debate/controversy was NOT fact check or newmakers claims. I reasoned that false/ unsupported claims were MORE controversial and likely to be debated! That's why I eliminated D. It made sense that a journalist wouldn't check quote veracity to get viewers to react/debate to ridiculously false claims.

I guess I overlooked 'A' thinking a disputed claim by a publication/journalist wouldn't be enough of an explanation as to why a journalist would not fact check claims. I was so sure of D being the answer. When I'm so confident of the answer and it makes sense to me on both the first try and blind review, I get deeply discouraged and just feel dumb. Lol.

With the Grace of the almighty and powerful God, I will score no less than 163 on the LSAT this January. I pray for all my fellow future counselors. We just have to remain consistent and hungry. Ask God to bring you confidence and trust in his will for your journey. We must stay hungry, team. We improve, incrementally each day. As Brad said, do not deprive the world of you God given talents and purpose!