The B's and C's didn't have adjustable cowl flaps from what I've seen, they had shutters ahead of the cooler. Here's a B (note the Jerico trumpet and MG ports faired over) and you can see the oil cooler's cowl lacks the flaps. The first photo in this post is also a B...you can see the shutters closed in front of the oil cooler. I believe that they eliminated the shutters and replaced them with the flaps on the D series.
Thanks Dave, I did a little looking into this and the early B-1s had the shutters and fixed cowl flaps, but things got a little confusing because mid production B-1s disposed of the fixed cowl flaps and went for separate leaves, whereas the very first production B-2s had the fixed cowl, but predominantly had the separate leaves, along with the R and C as you pointed out. The B-2s had a deeper radiator than the B-1s and ejector exhausts, whereas the first lot of B-1s just had ports, like the second image you posted; the top image is an early production B-2.
Here's an R, showing the separate leaves and ejector exhausts fitted to late model B-2s;