This Celtic symbol of everlasting love is formed from two triskeles. The triskeles, three cornered knots, denote the three aspects of two people, body, mind and spirit. The two triskeles, joined together, show a circle, the everlasting circle of eternity.
All the others are weak acids. A strong acid is one that dissociates completely when it dissolves in water. Dissociate means that the substance splits apart into ions. There are only a few strong acids in water, they are: HBr, HCl, HI, HNO3, HClO4 and H2SO4 (for the first H only) All other acids are weak acids. Chemists use the term strong or weak with regard to acids and bases to tell how much the substance dissociates in water.
You can compare the strength of the hydrogen bonding by comparing the electronegativities of the other elements. All the four elements, Br, F, Cl and I belong to the same group in the periodic table: group 17 named halogens. Then the kind of bonding they form is similar: polar covalent. You must know the trend of the electronegativities in the periodic table. Electronegativity decrease when you down across a group. Then the electronegativity of F is the higher of the group (indeed, it is the highest of all the 118 elements) . The higher the electronegativity the stronger the attraction that the halogen attracts the electrons and the stronger the hydorgen bonding. Then, the conclusion is that HF has the strongest hydrogen bonding.