AR 11850 IRIS observations of raster 1 (the field of view is indicated in Fig. 1, right panel). Top and middle panels from left to right: Mg II spectroheliograms at 2800.0 Å, 2803.5 Å, 2803.7 Å  and 2804.5 Å. Bottom left panel: spectroheliogram in the continuum at 2831.1 Å. Bottom right panel: spectroheliogram in Si V line. White or dark boxes show the selected CBs from A to D (the numbers in parenthesis indicate the hot explosions of Peter et al. 2014), small white circles with numbers 5 to 9 in the second row, right panel are examples of small brightenings.